Googletest export
Move all docs into top-level docs/ directory PiperOrigin-RevId: 350211277
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Abseil Team
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# Community-Created Documentation
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go/gunit-community-created-docs
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The following is a list, in no particular order, of links to documentation
|
||||
created by the Googletest community.
|
||||
|
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* [Googlemock Insights](https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles/blob/master/googletest/insights.md),
|
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by [ElectricRCAircraftGuy](https://github.com/ElectricRCAircraftGuy)
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docs/faq.md
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# Googletest FAQ
|
||||
|
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<!-- GOOGLETEST_CM0014 DO NOT DELETE -->
|
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|
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<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
## Why should test suite names and test names not contain underscore?
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||||
|
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Note: Googletest reserves underscore (`_`) for special purpose keywords, such as
|
||||
[the `DISABLED_` prefix](advanced.md#temporarily-disabling-tests), in addition
|
||||
to the following rationale.
|
||||
|
||||
Underscore (`_`) is special, as C++ reserves the following to be used by the
|
||||
compiler and the standard library:
|
||||
|
||||
1. any identifier that starts with an `_` followed by an upper-case letter, and
|
||||
2. any identifier that contains two consecutive underscores (i.e. `__`)
|
||||
*anywhere* in its name.
|
||||
|
||||
User code is *prohibited* from using such identifiers.
|
||||
|
||||
Now let's look at what this means for `TEST` and `TEST_F`.
|
||||
|
||||
Currently `TEST(TestSuiteName, TestName)` generates a class named
|
||||
`TestSuiteName_TestName_Test`. What happens if `TestSuiteName` or `TestName`
|
||||
contains `_`?
|
||||
|
||||
1. If `TestSuiteName` starts with an `_` followed by an upper-case letter (say,
|
||||
`_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus
|
||||
invalid.
|
||||
2. If `TestSuiteName` ends with an `_` (say, `Foo_`), we get
|
||||
`Foo__TestName_Test`, which is invalid.
|
||||
3. If `TestName` starts with an `_` (say, `_Bar`), we get
|
||||
`TestSuiteName__Bar_Test`, which is invalid.
|
||||
4. If `TestName` ends with an `_` (say, `Bar_`), we get
|
||||
`TestSuiteName_Bar__Test`, which is invalid.
|
||||
|
||||
So clearly `TestSuiteName` and `TestName` cannot start or end with `_`
|
||||
(Actually, `TestSuiteName` can start with `_` -- as long as the `_` isn't
|
||||
followed by an upper-case letter. But that's getting complicated. So for
|
||||
simplicity we just say that it cannot start with `_`.).
|
||||
|
||||
It may seem fine for `TestSuiteName` and `TestName` to contain `_` in the
|
||||
middle. However, consider this:
|
||||
|
||||
```c++
|
||||
TEST(Time, Flies_Like_An_Arrow) { ... }
|
||||
TEST(Time_Flies, Like_An_Arrow) { ... }
|
||||
```
|
||||
|
||||
Now, the two `TEST`s will both generate the same class
|
||||
(`Time_Flies_Like_An_Arrow_Test`). That's not good.
|
||||
|
||||
So for simplicity, we just ask the users to avoid `_` in `TestSuiteName` and
|
||||
`TestName`. The rule is more constraining than necessary, but it's simple and
|
||||
easy to remember. It also gives googletest some wiggle room in case its
|
||||
implementation needs to change in the future.
|
||||
|
||||
If you violate the rule, there may not be immediate consequences, but your test
|
||||
may (just may) break with a new compiler (or a new version of the compiler you
|
||||
are using) or with a new version of googletest. Therefore it's best to follow
|
||||
the rule.
|
||||
|
||||
## Why does googletest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`?
|
||||
|
||||
First of all you can use `EXPECT_NE(nullptr, ptr)` and `ASSERT_NE(nullptr,
|
||||
ptr)`. This is the preferred syntax in the style guide because nullptr does not
|
||||
have the type problems that NULL does. Which is why NULL does not work.
|
||||
|
||||
Due to some peculiarity of C++, it requires some non-trivial template meta
|
||||
programming tricks to support using `NULL` as an argument of the `EXPECT_XX()`
|
||||
and `ASSERT_XX()` macros. Therefore we only do it where it's most needed
|
||||
(otherwise we make the implementation of googletest harder to maintain and more
|
||||
error-prone than necessary).
|
||||
|
||||
The `EXPECT_EQ()` macro takes the *expected* value as its first argument and the
|
||||
*actual* value as the second. It's reasonable that someone wants to write
|
||||
`EXPECT_EQ(NULL, some_expression)`, and this indeed was requested several times.
|
||||
Therefore we implemented it.
|
||||
|
||||
The need for `EXPECT_NE(NULL, ptr)` isn't nearly as strong. When the assertion
|
||||
fails, you already know that `ptr` must be `NULL`, so it doesn't add any
|
||||
information to print `ptr` in this case. That means `EXPECT_TRUE(ptr != NULL)`
|
||||
works just as well.
|
||||
|
||||
If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'll have to
|
||||
support `EXPECT_NE(ptr, NULL)` as well, as unlike `EXPECT_EQ`, we don't have a
|
||||
convention on the order of the two arguments for `EXPECT_NE`. This means using
|
||||
the template meta programming tricks twice in the implementation, making it even
|
||||
harder to understand and maintain. We believe the benefit doesn't justify the
|
||||
cost.
|
||||
|
||||
Finally, with the growth of the gMock matcher library, we are encouraging people
|
||||
to use the unified `EXPECT_THAT(value, matcher)` syntax more often in tests. One
|
||||
significant advantage of the matcher approach is that matchers can be easily
|
||||
combined to form new matchers, while the `EXPECT_NE`, etc, macros cannot be
|
||||
easily combined. Therefore we want to invest more in the matchers than in the
|
||||
`EXPECT_XX()` macros.
|
||||
|
||||
## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests?
|
||||
|
||||
For testing various implementations of the same interface, either typed tests or
|
||||
value-parameterized tests can get it done. It's really up to you the user to
|
||||
decide which is more convenient for you, depending on your particular case. Some
|
||||
rough guidelines:
|
||||
|
||||
* Typed tests can be easier to write if instances of the different
|
||||
implementations can be created the same way, modulo the type. For example,
|
||||
if all these implementations have a public default constructor (such that
|
||||
you can write `new TypeParam`), or if their factory functions have the same
|
||||
form (e.g. `CreateInstance<TypeParam>()`).
|
||||
* Value-parameterized tests can be easier to write if you need different code
|
||||
patterns to create different implementations' instances, e.g. `new Foo` vs
|
||||
`new Bar(5)`. To accommodate for the differences, you can write factory
|
||||
function wrappers and pass these function pointers to the tests as their
|
||||
parameters.
|
||||
* When a typed test fails, the default output includes the name of the type,
|
||||
which can help you quickly identify which implementation is wrong.
|
||||
Value-parameterized tests only show the number of the failed iteration by
|
||||
default. You will need to define a function that returns the iteration name
|
||||
and pass it as the third parameter to INSTANTIATE_TEST_SUITE_P to have more
|
||||
useful output.
|
||||
* When using typed tests, you need to make sure you are testing against the
|
||||
interface type, not the concrete types (in other words, you want to make
|
||||
sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that
|
||||
`my_concrete_impl` works). It's less likely to make mistakes in this area
|
||||
when using value-parameterized tests.
|
||||
|
||||
I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give
|
||||
both approaches a try. Practice is a much better way to grasp the subtle
|
||||
differences between the two tools. Once you have some concrete experience, you
|
||||
can much more easily decide which one to use the next time.
|
||||
|
||||
## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help!
|
||||
|
||||
**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated*
|
||||
now. Please use `EqualsProto`, etc instead.
|
||||
|
||||
`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and
|
||||
are now less tolerant of invalid protocol buffer definitions. In particular, if
|
||||
you have a `foo.proto` that doesn't fully qualify the type of a protocol message
|
||||
it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you
|
||||
will now get run-time errors like:
|
||||
|
||||
```
|
||||
... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto":
|
||||
... descriptor.cc:...] blah.MyMessage.my_field: ".Bar" is not defined.
|
||||
```
|
||||
|
||||
If you see this, your `.proto` file is broken and needs to be fixed by making
|
||||
the types fully qualified. The new definition of `ProtocolMessageEquals` and
|
||||
`ProtocolMessageEquiv` just happen to reveal your bug.
|
||||
|
||||
## My death test modifies some state, but the change seems lost after the death test finishes. Why?
|
||||
|
||||
Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
|
||||
expected crash won't kill the test program (i.e. the parent process). As a
|
||||
result, any in-memory side effects they incur are observable in their respective
|
||||
sub-processes, but not in the parent process. You can think of them as running
|
||||
in a parallel universe, more or less.
|
||||
|
||||
In particular, if you use mocking and the death test statement invokes some mock
|
||||
methods, the parent process will think the calls have never occurred. Therefore,
|
||||
you may want to move your `EXPECT_CALL` statements inside the `EXPECT_DEATH`
|
||||
macro.
|
||||
|
||||
## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug?
|
||||
|
||||
Actually, the bug is in `htonl()`.
|
||||
|
||||
According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to
|
||||
use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as
|
||||
a *macro*, which breaks this usage.
|
||||
|
||||
Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not*
|
||||
standard C++. That hacky implementation has some ad hoc limitations. In
|
||||
particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo`
|
||||
is a template that has an integral argument.
|
||||
|
||||
The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a
|
||||
template argument, and thus doesn't compile in opt mode when `a` contains a call
|
||||
to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as
|
||||
the solution must work with different compilers on various platforms.
|
||||
|
||||
`htonl()` has some other problems as described in `//util/endian/endian.h`,
|
||||
which defines `ghtonl()` to replace it. `ghtonl()` does the same thing `htonl()`
|
||||
does, only without its problems. We suggest you to use `ghtonl()` instead of
|
||||
`htonl()`, both in your tests and production code.
|
||||
|
||||
`//util/endian/endian.h` also defines `ghtons()`, which solves similar problems
|
||||
in `htons()`.
|
||||
|
||||
Don't forget to add `//util/endian` to the list of dependencies in the `BUILD`
|
||||
file wherever `ghtonl()` and `ghtons()` are used. The library consists of a
|
||||
single header file and will not bloat your binary.
|
||||
|
||||
## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong?
|
||||
|
||||
If your class has a static data member:
|
||||
|
||||
```c++
|
||||
// foo.h
|
||||
class Foo {
|
||||
...
|
||||
static const int kBar = 100;
|
||||
};
|
||||
```
|
||||
|
||||
You also need to define it *outside* of the class body in `foo.cc`:
|
||||
|
||||
```c++
|
||||
const int Foo::kBar; // No initializer here.
|
||||
```
|
||||
|
||||
Otherwise your code is **invalid C++**, and may break in unexpected ways. In
|
||||
particular, using it in googletest comparison assertions (`EXPECT_EQ`, etc) will
|
||||
generate an "undefined reference" linker error. The fact that "it used to work"
|
||||
doesn't mean it's valid. It just means that you were lucky. :-)
|
||||
|
||||
If the declaration of the static data member is `constexpr` then it is
|
||||
implicitly an `inline` definition, and a separate definition in `foo.cc` is not
|
||||
needed:
|
||||
|
||||
```c++
|
||||
// foo.h
|
||||
class Foo {
|
||||
...
|
||||
static constexpr int kBar = 100; // Defines kBar, no need to do it in foo.cc.
|
||||
};
|
||||
```
|
||||
|
||||
## Can I derive a test fixture from another?
|
||||
|
||||
Yes.
|
||||
|
||||
Each test fixture has a corresponding and same named test suite. This means only
|
||||
one test suite can use a particular fixture. Sometimes, however, multiple test
|
||||
cases may want to use the same or slightly different fixtures. For example, you
|
||||
may want to make sure that all of a GUI library's test suites don't leak
|
||||
important system resources like fonts and brushes.
|
||||
|
||||
In googletest, you share a fixture among test suites by putting the shared logic
|
||||
in a base test fixture, then deriving from that base a separate fixture for each
|
||||
test suite that wants to use this common logic. You then use `TEST_F()` to write
|
||||
tests using each derived fixture.
|
||||
|
||||
Typically, your code looks like this:
|
||||
|
||||
```c++
|
||||
// Defines a base test fixture.
|
||||
class BaseTest : public ::testing::Test {
|
||||
protected:
|
||||
...
|
||||
};
|
||||
|
||||
// Derives a fixture FooTest from BaseTest.
|
||||
class FooTest : public BaseTest {
|
||||
protected:
|
||||
void SetUp() override {
|
||||
BaseTest::SetUp(); // Sets up the base fixture first.
|
||||
... additional set-up work ...
|
||||
}
|
||||
|
||||
void TearDown() override {
|
||||
... clean-up work for FooTest ...
|
||||
BaseTest::TearDown(); // Remember to tear down the base fixture
|
||||
// after cleaning up FooTest!
|
||||
}
|
||||
|
||||
... functions and variables for FooTest ...
|
||||
};
|
||||
|
||||
// Tests that use the fixture FooTest.
|
||||
TEST_F(FooTest, Bar) { ... }
|
||||
TEST_F(FooTest, Baz) { ... }
|
||||
|
||||
... additional fixtures derived from BaseTest ...
|
||||
```
|
||||
|
||||
If necessary, you can continue to derive test fixtures from a derived fixture.
|
||||
googletest has no limit on how deep the hierarchy can be.
|
||||
|
||||
For a complete example using derived test fixtures, see
|
||||
[sample5_unittest.cc](../googletest/samples/sample5_unittest.cc).
|
||||
|
||||
## My compiler complains "void value not ignored as it ought to be." What does this mean?
|
||||
|
||||
You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
|
||||
`ASSERT_*()` can only be used in `void` functions, due to exceptions being
|
||||
disabled by our build system. Please see more details
|
||||
[here](advanced.md#assertion-placement).
|
||||
|
||||
## My death test hangs (or seg-faults). How do I fix it?
|
||||
|
||||
In googletest, death tests are run in a child process and the way they work is
|
||||
delicate. To write death tests you really need to understand how they work.
|
||||
Please make sure you have read [this](advanced.md#how-it-works).
|
||||
|
||||
In particular, death tests don't like having multiple threads in the parent
|
||||
process. So the first thing you can try is to eliminate creating threads outside
|
||||
of `EXPECT_DEATH()`. For example, you may want to use mocks or fake objects
|
||||
instead of real ones in your tests.
|
||||
|
||||
Sometimes this is impossible as some library you must use may be creating
|
||||
threads before `main()` is even reached. In this case, you can try to minimize
|
||||
the chance of conflicts by either moving as many activities as possible inside
|
||||
`EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
|
||||
leaving as few things as possible in it. Also, you can try to set the death test
|
||||
style to `"threadsafe"`, which is safer but slower, and see if it helps.
|
||||
|
||||
If you go with thread-safe death tests, remember that they rerun the test
|
||||
program from the beginning in the child process. Therefore make sure your
|
||||
program can run side-by-side with itself and is deterministic.
|
||||
|
||||
In the end, this boils down to good concurrent programming. You have to make
|
||||
sure that there are no race conditions or deadlocks in your program. No silver
|
||||
bullet - sorry!
|
||||
|
||||
## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? {#CtorVsSetUp}
|
||||
|
||||
The first thing to remember is that googletest does **not** reuse the same test
|
||||
fixture object across multiple tests. For each `TEST_F`, googletest will create
|
||||
a **fresh** test fixture object, immediately call `SetUp()`, run the test body,
|
||||
call `TearDown()`, and then delete the test fixture object.
|
||||
|
||||
When you need to write per-test set-up and tear-down logic, you have the choice
|
||||
between using the test fixture constructor/destructor or `SetUp()/TearDown()`.
|
||||
The former is usually preferred, as it has the following benefits:
|
||||
|
||||
* By initializing a member variable in the constructor, we have the option to
|
||||
make it `const`, which helps prevent accidental changes to its value and
|
||||
makes the tests more obviously correct.
|
||||
* In case we need to subclass the test fixture class, the subclass'
|
||||
constructor is guaranteed to call the base class' constructor *first*, and
|
||||
the subclass' destructor is guaranteed to call the base class' destructor
|
||||
*afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of
|
||||
forgetting to call the base class' `SetUp()/TearDown()` or call them at the
|
||||
wrong time.
|
||||
|
||||
You may still want to use `SetUp()/TearDown()` in the following cases:
|
||||
|
||||
* C++ does not allow virtual function calls in constructors and destructors.
|
||||
You can call a method declared as virtual, but it will not use dynamic
|
||||
dispatch, it will use the definition from the class the constructor of which
|
||||
is currently executing. This is because calling a virtual method before the
|
||||
derived class constructor has a chance to run is very dangerous - the
|
||||
virtual method might operate on uninitialized data. Therefore, if you need
|
||||
to call a method that will be overridden in a derived class, you have to use
|
||||
`SetUp()/TearDown()`.
|
||||
* In the body of a constructor (or destructor), it's not possible to use the
|
||||
`ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal
|
||||
test failure that should prevent the test from running, it's necessary to
|
||||
use `abort` <!-- GOOGLETEST_CM0015 DO NOT DELETE --> and abort the whole test executable,
|
||||
or to use `SetUp()` instead of a constructor.
|
||||
* If the tear-down operation could throw an exception, you must use
|
||||
`TearDown()` as opposed to the destructor, as throwing in a destructor leads
|
||||
to undefined behavior and usually will kill your program right away. Note
|
||||
that many standard libraries (like STL) may throw when exceptions are
|
||||
enabled in the compiler. Therefore you should prefer `TearDown()` if you
|
||||
want to write portable tests that work with or without exceptions.
|
||||
* The googletest team is considering making the assertion macros throw on
|
||||
platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux
|
||||
client-side), which will eliminate the need for the user to propagate
|
||||
failures from a subroutine to its caller. Therefore, you shouldn't use
|
||||
googletest assertions in a destructor if your code could run on such a
|
||||
platform.
|
||||
|
||||
## The compiler complains "no matching function to call" when I use ASSERT_PRED*. How do I fix it?
|
||||
|
||||
If the predicate function you use in `ASSERT_PRED*` or `EXPECT_PRED*` is
|
||||
overloaded or a template, the compiler will have trouble figuring out which
|
||||
overloaded version it should use. `ASSERT_PRED_FORMAT*` and
|
||||
`EXPECT_PRED_FORMAT*` don't have this problem.
|
||||
|
||||
If you see this error, you might want to switch to
|
||||
`(ASSERT|EXPECT)_PRED_FORMAT*`, which will also give you a better failure
|
||||
message. If, however, that is not an option, you can resolve the problem by
|
||||
explicitly telling the compiler which version to pick.
|
||||
|
||||
For example, suppose you have
|
||||
|
||||
```c++
|
||||
bool IsPositive(int n) {
|
||||
return n > 0;
|
||||
}
|
||||
|
||||
bool IsPositive(double x) {
|
||||
return x > 0;
|
||||
}
|
||||
```
|
||||
|
||||
you will get a compiler error if you write
|
||||
|
||||
```c++
|
||||
EXPECT_PRED1(IsPositive, 5);
|
||||
```
|
||||
|
||||
However, this will work:
|
||||
|
||||
```c++
|
||||
EXPECT_PRED1(static_cast<bool (*)(int)>(IsPositive), 5);
|
||||
```
|
||||
|
||||
(The stuff inside the angled brackets for the `static_cast` operator is the type
|
||||
of the function pointer for the `int`-version of `IsPositive()`.)
|
||||
|
||||
As another example, when you have a template function
|
||||
|
||||
```c++
|
||||
template <typename T>
|
||||
bool IsNegative(T x) {
|
||||
return x < 0;
|
||||
}
|
||||
```
|
||||
|
||||
you can use it in a predicate assertion like this:
|
||||
|
||||
```c++
|
||||
ASSERT_PRED1(IsNegative<int>, -5);
|
||||
```
|
||||
|
||||
Things are more interesting if your template has more than one parameter. The
|
||||
following won't compile:
|
||||
|
||||
```c++
|
||||
ASSERT_PRED2(GreaterThan<int, int>, 5, 0);
|
||||
```
|
||||
|
||||
as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments, which
|
||||
is one more than expected. The workaround is to wrap the predicate function in
|
||||
parentheses:
|
||||
|
||||
```c++
|
||||
ASSERT_PRED2((GreaterThan<int, int>), 5, 0);
|
||||
```
|
||||
|
||||
## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why?
|
||||
|
||||
Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
|
||||
instead of
|
||||
|
||||
```c++
|
||||
return RUN_ALL_TESTS();
|
||||
```
|
||||
|
||||
they write
|
||||
|
||||
```c++
|
||||
RUN_ALL_TESTS();
|
||||
```
|
||||
|
||||
This is **wrong and dangerous**. The testing services needs to see the return
|
||||
value of `RUN_ALL_TESTS()` in order to determine if a test has passed. If your
|
||||
`main()` function ignores it, your test will be considered successful even if it
|
||||
has a googletest assertion failure. Very bad.
|
||||
|
||||
We have decided to fix this (thanks to Michael Chastain for the idea). Now, your
|
||||
code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with
|
||||
`gcc`. If you do so, you'll get a compiler error.
|
||||
|
||||
If you see the compiler complaining about you ignoring the return value of
|
||||
`RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the
|
||||
return value of `main()`.
|
||||
|
||||
But how could we introduce a change that breaks existing tests? Well, in this
|
||||
case, the code was already broken in the first place, so we didn't break it. :-)
|
||||
|
||||
## My compiler complains that a constructor (or destructor) cannot return a value. What's going on?
|
||||
|
||||
Due to a peculiarity of C++, in order to support the syntax for streaming
|
||||
messages to an `ASSERT_*`, e.g.
|
||||
|
||||
```c++
|
||||
ASSERT_EQ(1, Foo()) << "blah blah" << foo;
|
||||
```
|
||||
|
||||
we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
|
||||
`ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
|
||||
content of your constructor/destructor to a private void member function, or
|
||||
switch to `EXPECT_*()` if that works. This
|
||||
[section](advanced.md#assertion-placement) in the user's guide explains it.
|
||||
|
||||
## My SetUp() function is not called. Why?
|
||||
|
||||
C++ is case-sensitive. Did you spell it as `Setup()`?
|
||||
|
||||
Similarly, sometimes people spell `SetUpTestSuite()` as `SetupTestSuite()` and
|
||||
wonder why it's never called.
|
||||
|
||||
|
||||
## I have several test suites which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious.
|
||||
|
||||
You don't have to. Instead of
|
||||
|
||||
```c++
|
||||
class FooTest : public BaseTest {};
|
||||
|
||||
TEST_F(FooTest, Abc) { ... }
|
||||
TEST_F(FooTest, Def) { ... }
|
||||
|
||||
class BarTest : public BaseTest {};
|
||||
|
||||
TEST_F(BarTest, Abc) { ... }
|
||||
TEST_F(BarTest, Def) { ... }
|
||||
```
|
||||
|
||||
you can simply `typedef` the test fixtures:
|
||||
|
||||
```c++
|
||||
typedef BaseTest FooTest;
|
||||
|
||||
TEST_F(FooTest, Abc) { ... }
|
||||
TEST_F(FooTest, Def) { ... }
|
||||
|
||||
typedef BaseTest BarTest;
|
||||
|
||||
TEST_F(BarTest, Abc) { ... }
|
||||
TEST_F(BarTest, Def) { ... }
|
||||
```
|
||||
|
||||
## googletest output is buried in a whole bunch of LOG messages. What do I do?
|
||||
|
||||
The googletest output is meant to be a concise and human-friendly report. If
|
||||
your test generates textual output itself, it will mix with the googletest
|
||||
output, making it hard to read. However, there is an easy solution to this
|
||||
problem.
|
||||
|
||||
Since `LOG` messages go to stderr, we decided to let googletest output go to
|
||||
stdout. This way, you can easily separate the two using redirection. For
|
||||
example:
|
||||
|
||||
```shell
|
||||
$ ./my_test > gtest_output.txt
|
||||
```
|
||||
|
||||
## Why should I prefer test fixtures over global variables?
|
||||
|
||||
There are several good reasons:
|
||||
|
||||
1. It's likely your test needs to change the states of its global variables.
|
||||
This makes it difficult to keep side effects from escaping one test and
|
||||
contaminating others, making debugging difficult. By using fixtures, each
|
||||
test has a fresh set of variables that's different (but with the same
|
||||
names). Thus, tests are kept independent of each other.
|
||||
2. Global variables pollute the global namespace.
|
||||
3. Test fixtures can be reused via subclassing, which cannot be done easily
|
||||
with global variables. This is useful if many test suites have something in
|
||||
common.
|
||||
|
||||
## What can the statement argument in ASSERT_DEATH() be?
|
||||
|
||||
`ASSERT_DEATH(statement, matcher)` (or any death assertion macro) can be used
|
||||
wherever *`statement`* is valid. So basically *`statement`* can be any C++
|
||||
statement that makes sense in the current context. In particular, it can
|
||||
reference global and/or local variables, and can be:
|
||||
|
||||
* a simple function call (often the case),
|
||||
* a complex expression, or
|
||||
* a compound statement.
|
||||
|
||||
Some examples are shown here:
|
||||
|
||||
```c++
|
||||
// A death test can be a simple function call.
|
||||
TEST(MyDeathTest, FunctionCall) {
|
||||
ASSERT_DEATH(Xyz(5), "Xyz failed");
|
||||
}
|
||||
|
||||
// Or a complex expression that references variables and functions.
|
||||
TEST(MyDeathTest, ComplexExpression) {
|
||||
const bool c = Condition();
|
||||
ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
|
||||
"(Func1|Method) failed");
|
||||
}
|
||||
|
||||
// Death assertions can be used anywhere in a function. In
|
||||
// particular, they can be inside a loop.
|
||||
TEST(MyDeathTest, InsideLoop) {
|
||||
// Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
|
||||
for (int i = 0; i < 5; i++) {
|
||||
EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
|
||||
::testing::Message() << "where i is " << i);
|
||||
}
|
||||
}
|
||||
|
||||
// A death assertion can contain a compound statement.
|
||||
TEST(MyDeathTest, CompoundStatement) {
|
||||
// Verifies that at lease one of Bar(0), Bar(1), ..., and
|
||||
// Bar(4) dies.
|
||||
ASSERT_DEATH({
|
||||
for (int i = 0; i < 5; i++) {
|
||||
Bar(i);
|
||||
}
|
||||
},
|
||||
"Bar has \\d+ errors");
|
||||
}
|
||||
```
|
||||
|
||||
gtest-death-test_test.cc contains more examples if you are interested.
|
||||
|
||||
## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why?
|
||||
|
||||
Googletest needs to be able to create objects of your test fixture class, so it
|
||||
must have a default constructor. Normally the compiler will define one for you.
|
||||
However, there are cases where you have to define your own:
|
||||
|
||||
* If you explicitly declare a non-default constructor for class `FooTest`
|
||||
(`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a
|
||||
default constructor, even if it would be empty.
|
||||
* If `FooTest` has a const non-static data member, then you have to define the
|
||||
default constructor *and* initialize the const member in the initializer
|
||||
list of the constructor. (Early versions of `gcc` doesn't force you to
|
||||
initialize the const member. It's a bug that has been fixed in `gcc 4`.)
|
||||
|
||||
## Why does ASSERT_DEATH complain about previous threads that were already joined?
|
||||
|
||||
With the Linux pthread library, there is no turning back once you cross the line
|
||||
from a single thread to multiple threads. The first time you create a thread, a
|
||||
manager thread is created in addition, so you get 3, not 2, threads. Later when
|
||||
the thread you create joins the main thread, the thread count decrements by 1,
|
||||
but the manager thread will never be killed, so you still have 2 threads, which
|
||||
means you cannot safely run a death test.
|
||||
|
||||
The new NPTL thread library doesn't suffer from this problem, as it doesn't
|
||||
create a manager thread. However, if you don't control which machine your test
|
||||
runs on, you shouldn't depend on this.
|
||||
|
||||
## Why does googletest require the entire test suite, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH?
|
||||
|
||||
googletest does not interleave tests from different test suites. That is, it
|
||||
runs all tests in one test suite first, and then runs all tests in the next test
|
||||
suite, and so on. googletest does this because it needs to set up a test suite
|
||||
before the first test in it is run, and tear it down afterwards. Splitting up
|
||||
the test case would require multiple set-up and tear-down processes, which is
|
||||
inefficient and makes the semantics unclean.
|
||||
|
||||
If we were to determine the order of tests based on test name instead of test
|
||||
case name, then we would have a problem with the following situation:
|
||||
|
||||
```c++
|
||||
TEST_F(FooTest, AbcDeathTest) { ... }
|
||||
TEST_F(FooTest, Uvw) { ... }
|
||||
|
||||
TEST_F(BarTest, DefDeathTest) { ... }
|
||||
TEST_F(BarTest, Xyz) { ... }
|
||||
```
|
||||
|
||||
Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
|
||||
interleave tests from different test suites, we need to run all tests in the
|
||||
`FooTest` case before running any test in the `BarTest` case. This contradicts
|
||||
with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
|
||||
|
||||
## But I don't like calling my entire test suite \*DeathTest when it contains both death tests and non-death tests. What do I do?
|
||||
|
||||
You don't have to, but if you like, you may split up the test suite into
|
||||
`FooTest` and `FooDeathTest`, where the names make it clear that they are
|
||||
related:
|
||||
|
||||
```c++
|
||||
class FooTest : public ::testing::Test { ... };
|
||||
|
||||
TEST_F(FooTest, Abc) { ... }
|
||||
TEST_F(FooTest, Def) { ... }
|
||||
|
||||
using FooDeathTest = FooTest;
|
||||
|
||||
TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
|
||||
TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
|
||||
```
|
||||
|
||||
## googletest prints the LOG messages in a death test's child process only when the test fails. How can I see the LOG messages when the death test succeeds?
|
||||
|
||||
Printing the LOG messages generated by the statement inside `EXPECT_DEATH()`
|
||||
makes it harder to search for real problems in the parent's log. Therefore,
|
||||
googletest only prints them when the death test has failed.
|
||||
|
||||
If you really need to see such LOG messages, a workaround is to temporarily
|
||||
break the death test (e.g. by changing the regex pattern it is expected to
|
||||
match). Admittedly, this is a hack. We'll consider a more permanent solution
|
||||
after the fork-and-exec-style death tests are implemented.
|
||||
|
||||
## The compiler complains about "no match for 'operator<<'" when I use an assertion. What gives?
|
||||
|
||||
If you use a user-defined type `FooType` in an assertion, you must make sure
|
||||
there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
|
||||
defined such that we can print a value of `FooType`.
|
||||
|
||||
In addition, if `FooType` is declared in a name space, the `<<` operator also
|
||||
needs to be defined in the *same* name space. See https://abseil.io/tips/49 for details.
|
||||
|
||||
## How do I suppress the memory leak messages on Windows?
|
||||
|
||||
Since the statically initialized googletest singleton requires allocations on
|
||||
the heap, the Visual C++ memory leak detector will report memory leaks at the
|
||||
end of the program run. The easiest way to avoid this is to use the
|
||||
`_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
|
||||
statically initialized heap objects. See MSDN for more details and additional
|
||||
heap check/debug routines.
|
||||
|
||||
## How can my code detect if it is running in a test?
|
||||
|
||||
If you write code that sniffs whether it's running in a test and does different
|
||||
things accordingly, you are leaking test-only logic into production code and
|
||||
there is no easy way to ensure that the test-only code paths aren't run by
|
||||
mistake in production. Such cleverness also leads to
|
||||
[Heisenbugs](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly
|
||||
advise against the practice, and googletest doesn't provide a way to do it.
|
||||
|
||||
In general, the recommended way to cause the code to behave differently under
|
||||
test is [Dependency Injection](https://en.wikipedia.org/wiki/Dependency_injection). You can inject
|
||||
different functionality from the test and from the production code. Since your
|
||||
production code doesn't link in the for-test logic at all (the
|
||||
[`testonly`](https://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) attribute for BUILD targets helps to ensure
|
||||
that), there is no danger in accidentally running it.
|
||||
|
||||
However, if you *really*, *really*, *really* have no choice, and if you follow
|
||||
the rule of ending your test program names with `_test`, you can use the
|
||||
*horrible* hack of sniffing your executable name (`argv[0]` in `main()`) to know
|
||||
whether the code is under test.
|
||||
|
||||
## How do I temporarily disable a test?
|
||||
|
||||
If you have a broken test that you cannot fix right away, you can add the
|
||||
DISABLED_ prefix to its name. This will exclude it from execution. This is
|
||||
better than commenting out the code or using #if 0, as disabled tests are still
|
||||
compiled (and thus won't rot).
|
||||
|
||||
To include disabled tests in test execution, just invoke the test program with
|
||||
the --gtest_also_run_disabled_tests flag.
|
||||
|
||||
## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces?
|
||||
|
||||
Yes.
|
||||
|
||||
The rule is **all test methods in the same test suite must use the same fixture
|
||||
class.** This means that the following is **allowed** because both tests use the
|
||||
same fixture class (`::testing::Test`).
|
||||
|
||||
```c++
|
||||
namespace foo {
|
||||
TEST(CoolTest, DoSomething) {
|
||||
SUCCEED();
|
||||
}
|
||||
} // namespace foo
|
||||
|
||||
namespace bar {
|
||||
TEST(CoolTest, DoSomething) {
|
||||
SUCCEED();
|
||||
}
|
||||
} // namespace bar
|
||||
```
|
||||
|
||||
However, the following code is **not allowed** and will produce a runtime error
|
||||
from googletest because the test methods are using different test fixture
|
||||
classes with the same test suite name.
|
||||
|
||||
```c++
|
||||
namespace foo {
|
||||
class CoolTest : public ::testing::Test {}; // Fixture foo::CoolTest
|
||||
TEST_F(CoolTest, DoSomething) {
|
||||
SUCCEED();
|
||||
}
|
||||
} // namespace foo
|
||||
|
||||
namespace bar {
|
||||
class CoolTest : public ::testing::Test {}; // Fixture: bar::CoolTest
|
||||
TEST_F(CoolTest, DoSomething) {
|
||||
SUCCEED();
|
||||
}
|
||||
} // namespace bar
|
||||
```
|
||||
786
docs/gmock_cheat_sheet.md
Normal file
786
docs/gmock_cheat_sheet.md
Normal file
@@ -0,0 +1,786 @@
|
||||
# gMock Cheat Sheet
|
||||
|
||||
<!-- GOOGLETEST_CM0019 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0033 DO NOT DELETE -->
|
||||
|
||||
## Defining a Mock Class
|
||||
|
||||
### Mocking a Normal Class {#MockClass}
|
||||
|
||||
Given
|
||||
|
||||
```cpp
|
||||
class Foo {
|
||||
...
|
||||
virtual ~Foo();
|
||||
virtual int GetSize() const = 0;
|
||||
virtual string Describe(const char* name) = 0;
|
||||
virtual string Describe(int type) = 0;
|
||||
virtual bool Process(Bar elem, int count) = 0;
|
||||
};
|
||||
```
|
||||
|
||||
(note that `~Foo()` **must** be virtual) we can define its mock as
|
||||
|
||||
```cpp
|
||||
#include "gmock/gmock.h"
|
||||
|
||||
class MockFoo : public Foo {
|
||||
...
|
||||
MOCK_METHOD(int, GetSize, (), (const, override));
|
||||
MOCK_METHOD(string, Describe, (const char* name), (override));
|
||||
MOCK_METHOD(string, Describe, (int type), (override));
|
||||
MOCK_METHOD(bool, Process, (Bar elem, int count), (override));
|
||||
};
|
||||
```
|
||||
|
||||
To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock,
|
||||
which warns on all uninteresting calls, or a "strict" mock, which treats them as
|
||||
failures:
|
||||
|
||||
```cpp
|
||||
using ::testing::NiceMock;
|
||||
using ::testing::NaggyMock;
|
||||
using ::testing::StrictMock;
|
||||
|
||||
NiceMock<MockFoo> nice_foo; // The type is a subclass of MockFoo.
|
||||
NaggyMock<MockFoo> naggy_foo; // The type is a subclass of MockFoo.
|
||||
StrictMock<MockFoo> strict_foo; // The type is a subclass of MockFoo.
|
||||
```
|
||||
|
||||
**Note:** A mock object is currently naggy by default. We may make it nice by
|
||||
default in the future.
|
||||
|
||||
### Mocking a Class Template {#MockTemplate}
|
||||
|
||||
Class templates can be mocked just like any class.
|
||||
|
||||
To mock
|
||||
|
||||
```cpp
|
||||
template <typename Elem>
|
||||
class StackInterface {
|
||||
...
|
||||
virtual ~StackInterface();
|
||||
virtual int GetSize() const = 0;
|
||||
virtual void Push(const Elem& x) = 0;
|
||||
};
|
||||
```
|
||||
|
||||
(note that all member functions that are mocked, including `~StackInterface()`
|
||||
**must** be virtual).
|
||||
|
||||
```cpp
|
||||
template <typename Elem>
|
||||
class MockStack : public StackInterface<Elem> {
|
||||
...
|
||||
MOCK_METHOD(int, GetSize, (), (const, override));
|
||||
MOCK_METHOD(void, Push, (const Elem& x), (override));
|
||||
};
|
||||
```
|
||||
|
||||
### Specifying Calling Conventions for Mock Functions
|
||||
|
||||
If your mock function doesn't use the default calling convention, you can
|
||||
specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter.
|
||||
For example,
|
||||
|
||||
```cpp
|
||||
MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE)));
|
||||
MOCK_METHOD(int, Bar, (double x, double y),
|
||||
(const, Calltype(STDMETHODCALLTYPE)));
|
||||
```
|
||||
|
||||
where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
|
||||
|
||||
## Using Mocks in Tests {#UsingMocks}
|
||||
|
||||
The typical work flow is:
|
||||
|
||||
1. Import the gMock names you need to use. All gMock symbols are in the
|
||||
`testing` namespace unless they are macros or otherwise noted.
|
||||
2. Create the mock objects.
|
||||
3. Optionally, set the default actions of the mock objects.
|
||||
4. Set your expectations on the mock objects (How will they be called? What
|
||||
will they do?).
|
||||
5. Exercise code that uses the mock objects; if necessary, check the result
|
||||
using googletest assertions.
|
||||
6. When a mock object is destructed, gMock automatically verifies that all
|
||||
expectations on it have been satisfied.
|
||||
|
||||
Here's an example:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return; // #1
|
||||
|
||||
TEST(BarTest, DoesThis) {
|
||||
MockFoo foo; // #2
|
||||
|
||||
ON_CALL(foo, GetSize()) // #3
|
||||
.WillByDefault(Return(1));
|
||||
// ... other default actions ...
|
||||
|
||||
EXPECT_CALL(foo, Describe(5)) // #4
|
||||
.Times(3)
|
||||
.WillRepeatedly(Return("Category 5"));
|
||||
// ... other expectations ...
|
||||
|
||||
EXPECT_EQ("good", MyProductionFunction(&foo)); // #5
|
||||
} // #6
|
||||
```
|
||||
|
||||
## Setting Default Actions {#OnCall}
|
||||
|
||||
gMock has a **built-in default action** for any function that returns `void`,
|
||||
`bool`, a numeric value, or a pointer. In C++11, it will additionally returns
|
||||
the default-constructed value, if one exists for the given type.
|
||||
|
||||
To customize the default action for functions with return type *`T`*:
|
||||
|
||||
```cpp
|
||||
using ::testing::DefaultValue;
|
||||
|
||||
// Sets the default value to be returned. T must be CopyConstructible.
|
||||
DefaultValue<T>::Set(value);
|
||||
// Sets a factory. Will be invoked on demand. T must be MoveConstructible.
|
||||
// T MakeT();
|
||||
DefaultValue<T>::SetFactory(&MakeT);
|
||||
// ... use the mocks ...
|
||||
// Resets the default value.
|
||||
DefaultValue<T>::Clear();
|
||||
```
|
||||
|
||||
Example usage:
|
||||
|
||||
```cpp
|
||||
// Sets the default action for return type std::unique_ptr<Buzz> to
|
||||
// creating a new Buzz every time.
|
||||
DefaultValue<std::unique_ptr<Buzz>>::SetFactory(
|
||||
[] { return MakeUnique<Buzz>(AccessLevel::kInternal); });
|
||||
|
||||
// When this fires, the default action of MakeBuzz() will run, which
|
||||
// will return a new Buzz object.
|
||||
EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber());
|
||||
|
||||
auto buzz1 = mock_buzzer_.MakeBuzz("hello");
|
||||
auto buzz2 = mock_buzzer_.MakeBuzz("hello");
|
||||
EXPECT_NE(nullptr, buzz1);
|
||||
EXPECT_NE(nullptr, buzz2);
|
||||
EXPECT_NE(buzz1, buzz2);
|
||||
|
||||
// Resets the default action for return type std::unique_ptr<Buzz>,
|
||||
// to avoid interfere with other tests.
|
||||
DefaultValue<std::unique_ptr<Buzz>>::Clear();
|
||||
```
|
||||
|
||||
To customize the default action for a particular method of a specific mock
|
||||
object, use `ON_CALL()`. `ON_CALL()` has a similar syntax to `EXPECT_CALL()`,
|
||||
but it is used for setting default behaviors (when you do not require that the
|
||||
mock method is called). See [here](gmock_cook_book.md#UseOnCall) for a more detailed
|
||||
discussion.
|
||||
|
||||
```cpp
|
||||
ON_CALL(mock-object, method(matchers))
|
||||
.With(multi-argument-matcher) ?
|
||||
.WillByDefault(action);
|
||||
```
|
||||
|
||||
## Setting Expectations {#ExpectCall}
|
||||
|
||||
`EXPECT_CALL()` sets **expectations** on a mock method (How will it be called?
|
||||
What will it do?):
|
||||
|
||||
```cpp
|
||||
EXPECT_CALL(mock-object, method (matchers)?)
|
||||
.With(multi-argument-matcher) ?
|
||||
.Times(cardinality) ?
|
||||
.InSequence(sequences) *
|
||||
.After(expectations) *
|
||||
.WillOnce(action) *
|
||||
.WillRepeatedly(action) ?
|
||||
.RetiresOnSaturation(); ?
|
||||
```
|
||||
|
||||
For each item above, `?` means it can be used at most once, while `*` means it
|
||||
can be used any number of times.
|
||||
|
||||
In order to pass, `EXPECT_CALL` must be used before the calls are actually made.
|
||||
|
||||
The `(matchers)` is a comma-separated list of matchers that correspond to each
|
||||
of the arguments of `method`, and sets the expectation only for calls of
|
||||
`method` that matches all of the matchers.
|
||||
|
||||
If `(matchers)` is omitted, the expectation is the same as if the matchers were
|
||||
set to anything matchers (for example, `(_, _, _, _)` for a four-arg method).
|
||||
|
||||
If `Times()` is omitted, the cardinality is assumed to be:
|
||||
|
||||
* `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`;
|
||||
* `Times(n)` when there are `n` `WillOnce()`s but no `WillRepeatedly()`, where
|
||||
`n` >= 1; or
|
||||
* `Times(AtLeast(n))` when there are `n` `WillOnce()`s and a
|
||||
`WillRepeatedly()`, where `n` >= 0.
|
||||
|
||||
A method with no `EXPECT_CALL()` is free to be invoked *any number of times*,
|
||||
and the default action will be taken each time.
|
||||
|
||||
## Matchers {#MatcherList}
|
||||
|
||||
<!-- GOOGLETEST_CM0020 DO NOT DELETE -->
|
||||
|
||||
A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or
|
||||
`EXPECT_CALL()`, or use it to validate a value directly using two macros:
|
||||
|
||||
<!-- mdformat off(github rendering does not support multiline tables) -->
|
||||
| Macro | Description |
|
||||
| :----------------------------------- | :------------------------------------ |
|
||||
| `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. |
|
||||
| `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
**Note:** Although equality matching via `EXPECT_THAT(actual_value,
|
||||
expected_value)` is supported, prefer to make the comparison explicit via
|
||||
`EXPECT_THAT(actual_value, Eq(expected_value))` or `EXPECT_EQ(actual_value,
|
||||
expected_value)`.
|
||||
|
||||
Built-in matchers (where `argument` is the function argument, e.g.
|
||||
`actual_value` in the example above, or when used in the context of
|
||||
`EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are
|
||||
divided into several categories:
|
||||
|
||||
### Wildcard
|
||||
|
||||
Matcher | Description
|
||||
:-------------------------- | :-----------------------------------------------
|
||||
`_` | `argument` can be any value of the correct type.
|
||||
`A<type>()` or `An<type>()` | `argument` can be any value of type `type`.
|
||||
|
||||
### Generic Comparison
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :--------------------- | :-------------------------------------------------- |
|
||||
| `Eq(value)` or `value` | `argument == value` |
|
||||
| `Ge(value)` | `argument >= value` |
|
||||
| `Gt(value)` | `argument > value` |
|
||||
| `Le(value)` | `argument <= value` |
|
||||
| `Lt(value)` | `argument < value` |
|
||||
| `Ne(value)` | `argument != value` |
|
||||
| `IsFalse()` | `argument` evaluates to `false` in a Boolean context. |
|
||||
| `IsTrue()` | `argument` evaluates to `true` in a Boolean context. |
|
||||
| `IsNull()` | `argument` is a `NULL` pointer (raw or smart). |
|
||||
| `NotNull()` | `argument` is a non-null pointer (raw or smart). |
|
||||
| `Optional(m)` | `argument` is `optional<>` that contains a value matching `m`. (For testing whether an `optional<>` is set, check for equality with `nullopt`. You may need to use `Eq(nullopt)` if the inner type doesn't have `==`.)|
|
||||
| `VariantWith<T>(m)` | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. |
|
||||
| `Ref(variable)` | `argument` is a reference to `variable`. |
|
||||
| `TypedEq<type>(value)` | `argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or
|
||||
destructed later. If the compiler complains that `value` doesn't have a public
|
||||
copy constructor, try wrap it in `std::ref()`, e.g.
|
||||
`Eq(std::ref(non_copyable_value))`. If you do that, make sure
|
||||
`non_copyable_value` is not changed afterwards, or the meaning of your matcher
|
||||
will be changed.
|
||||
|
||||
`IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types
|
||||
that can be explicitly converted to Boolean, but are not implicitly converted to
|
||||
Boolean. In other cases, you can use the basic
|
||||
[`EXPECT_TRUE` and `EXPECT_FALSE`](../../googletest/docs/primer#basic-assertions)
|
||||
assertions.
|
||||
|
||||
### Floating-Point Matchers {#FpMatchers}
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------------- | :--------------------------------- |
|
||||
| `DoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. |
|
||||
| `FloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. |
|
||||
| `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. |
|
||||
| `NanSensitiveFloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. |
|
||||
| `IsNan()` | `argument` is any floating-point type with a NaN value. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
The above matchers use ULP-based comparison (the same as used in googletest).
|
||||
They automatically pick a reasonable error bound based on the absolute value of
|
||||
the expected value. `DoubleEq()` and `FloatEq()` conform to the IEEE standard,
|
||||
which requires comparing two NaNs for equality to return false. The
|
||||
`NanSensitive*` version instead treats two NaNs as equal, which is often what a
|
||||
user wants.
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------------------------------ | :----------------------- |
|
||||
| `DoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
|
||||
| `FloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
|
||||
| `NanSensitiveDoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
|
||||
| `NanSensitiveFloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### String Matchers
|
||||
|
||||
The `argument` can be either a C string or a C++ string object:
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :---------------------- | :------------------------------------------------- |
|
||||
| `ContainsRegex(string)` | `argument` matches the given regular expression. |
|
||||
| `EndsWith(suffix)` | `argument` ends with string `suffix`. |
|
||||
| `HasSubstr(string)` | `argument` contains `string` as a sub-string. |
|
||||
| `MatchesRegex(string)` | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. |
|
||||
| `StartsWith(prefix)` | `argument` starts with string `prefix`. |
|
||||
| `StrCaseEq(string)` | `argument` is equal to `string`, ignoring case. |
|
||||
| `StrCaseNe(string)` | `argument` is not equal to `string`, ignoring case. |
|
||||
| `StrEq(string)` | `argument` is equal to `string`. |
|
||||
| `StrNe(string)` | `argument` is not equal to `string`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
`ContainsRegex()` and `MatchesRegex()` take ownership of the `RE` object. They
|
||||
use the regular expression syntax defined
|
||||
[here](../../googletest/docs/advanced.md#regular-expression-syntax). All of
|
||||
these matchers, except `ContainsRegex()` and `MatchesRegex()` work for wide
|
||||
strings as well.
|
||||
|
||||
### Container Matchers
|
||||
|
||||
Most STL-style containers support `==`, so you can use `Eq(expected_container)`
|
||||
or simply `expected_container` to match a container exactly. If you want to
|
||||
write the elements in-line, match them more flexibly, or get more informative
|
||||
messages, you can use:
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :---------------------------------------- | :------------------------------- |
|
||||
| `BeginEndDistanceIs(m)` | `argument` is a container whose `begin()` and `end()` iterators are separated by a number of increments matching `m`. E.g. `BeginEndDistanceIs(2)` or `BeginEndDistanceIs(Lt(2))`. For containers that define a `size()` method, `SizeIs(m)` may be more efficient. |
|
||||
| `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. |
|
||||
| `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. |
|
||||
| `Each(e)` | `argument` is a container where *every* element matches `e`, which can be either a value or a matcher. |
|
||||
| `ElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, where the *i*-th element matches `ei`, which can be a value or a matcher. |
|
||||
| `ElementsAreArray({e0, e1, ..., en})`, `ElementsAreArray(a_container)`, `ElementsAreArray(begin, end)`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
|
||||
| `IsEmpty()` | `argument` is an empty container (`container.empty()`). |
|
||||
| `IsSubsetOf({e0, e1, ..., en})`, `IsSubsetOf(a_container)`, `IsSubsetOf(begin, end)`, `IsSubsetOf(array)`, or `IsSubsetOf(array, count)` | `argument` matches `UnorderedElementsAre(x0, x1, ..., xk)` for some subset `{x0, x1, ..., xk}` of the expected matchers. |
|
||||
| `IsSupersetOf({e0, e1, ..., en})`, `IsSupersetOf(a_container)`, `IsSupersetOf(begin, end)`, `IsSupersetOf(array)`, or `IsSupersetOf(array, count)` | Some subset of `argument` matches `UnorderedElementsAre(`expected matchers`)`. |
|
||||
| `Pointwise(m, container)`, `Pointwise(m, {e0, e1, ..., en})` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. |
|
||||
| `SizeIs(m)` | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`. |
|
||||
| `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under *some* permutation of the elements, each element matches an `ei` (for a different `i`), which can be a value or a matcher. |
|
||||
| `UnorderedElementsAreArray({e0, e1, ..., en})`, `UnorderedElementsAreArray(a_container)`, `UnorderedElementsAreArray(begin, end)`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
|
||||
| `UnorderedPointwise(m, container)`, `UnorderedPointwise(m, {e0, e1, ..., en})` | Like `Pointwise(m, container)`, but ignores the order of elements. |
|
||||
| `WhenSorted(m)` | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(ElementsAre(1, 2, 3))` verifies that `argument` contains elements 1, 2, and 3, ignoring order. |
|
||||
| `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater(), ElementsAre(3, 2, 1))`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
**Notes:**
|
||||
|
||||
* These matchers can also match:
|
||||
1. a native array passed by reference (e.g. in `Foo(const int (&a)[5])`),
|
||||
and
|
||||
2. an array passed as a pointer and a count (e.g. in `Bar(const T* buffer,
|
||||
int len)` -- see [Multi-argument Matchers](#MultiArgMatchers)).
|
||||
* The array being matched may be multi-dimensional (i.e. its elements can be
|
||||
arrays).
|
||||
* `m` in `Pointwise(m, ...)` should be a matcher for `::std::tuple<T, U>`
|
||||
where `T` and `U` are the element type of the actual container and the
|
||||
expected container, respectively. For example, to compare two `Foo`
|
||||
containers where `Foo` doesn't support `operator==`, one might write:
|
||||
|
||||
```cpp
|
||||
using ::std::get;
|
||||
MATCHER(FooEq, "") {
|
||||
return std::get<0>(arg).Equals(std::get<1>(arg));
|
||||
}
|
||||
...
|
||||
EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos));
|
||||
```
|
||||
|
||||
### Member Matchers
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------------ | :----------------------------------------- |
|
||||
| `Field(&class::field, m)` | `argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. |
|
||||
| `Key(e)` | `argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`. |
|
||||
| `Pair(m1, m2)` | `argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. |
|
||||
| `FieldsAre(m...)` | `argument` is a compatible object where each field matches piecewise with `m...`. A compatible object is any that supports the `std::tuple_size<Obj>`+`get<I>(obj)` protocol. In C++17 and up this also supports types compatible with structured bindings, like aggregates. |
|
||||
| `Property(&class::property, m)` | `argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Matching the Result of a Function, Functor, or Callback
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :--------------- | :------------------------------------------------ |
|
||||
| `ResultOf(f, m)` | `f(argument)` matches matcher `m`, where `f` is a function or functor. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Pointer Matchers
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------ | :---------------------------------------------- |
|
||||
| `Address(m)` | the result of `std::addressof(argument)` matches `m`. |
|
||||
| `Pointee(m)` | `argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`. |
|
||||
| `Pointer(m)` | `argument` (either a smart pointer or a raw pointer) contains a pointer that matches `m`. `m` will match against the raw pointer regardless of the type of `argument`. |
|
||||
| `WhenDynamicCastTo<T>(m)` | when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
<!-- GOOGLETEST_CM0026 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0027 DO NOT DELETE -->
|
||||
|
||||
### Multi-argument Matchers {#MultiArgMatchers}
|
||||
|
||||
Technically, all matchers match a *single* value. A "multi-argument" matcher is
|
||||
just one that matches a *tuple*. The following matchers can be used to match a
|
||||
tuple `(x, y)`:
|
||||
|
||||
Matcher | Description
|
||||
:------ | :----------
|
||||
`Eq()` | `x == y`
|
||||
`Ge()` | `x >= y`
|
||||
`Gt()` | `x > y`
|
||||
`Le()` | `x <= y`
|
||||
`Lt()` | `x < y`
|
||||
`Ne()` | `x != y`
|
||||
|
||||
You can use the following selectors to pick a subset of the arguments (or
|
||||
reorder them) to participate in the matching:
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------- | :---------------------------------------------- |
|
||||
| `AllArgs(m)` | Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`. |
|
||||
| `Args<N1, N2, ..., Nk>(m)` | The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Composite Matchers
|
||||
|
||||
You can make a matcher from one or more other matchers:
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------------------------- | :-------------------------------------- |
|
||||
| `AllOf(m1, m2, ..., mn)` | `argument` matches all of the matchers `m1` to `mn`. |
|
||||
| `AllOfArray({m0, m1, ..., mn})`, `AllOfArray(a_container)`, `AllOfArray(begin, end)`, `AllOfArray(array)`, or `AllOfArray(array, count)` | The same as `AllOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
|
||||
| `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. |
|
||||
| `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
|
||||
| `Not(m)` | `argument` doesn't match matcher `m`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
<!-- GOOGLETEST_CM0028 DO NOT DELETE -->
|
||||
|
||||
### Adapters for Matchers
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :---------------------- | :------------------------------------ |
|
||||
| `MatcherCast<T>(m)` | casts matcher `m` to type `Matcher<T>`. |
|
||||
| `SafeMatcherCast<T>(m)` | [safely casts](gmock_cook_book.md#casting-matchers) matcher `m` to type `Matcher<T>`. |
|
||||
| `Truly(predicate)` | `predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
`AddressSatisfies(callback)` and `Truly(callback)` take ownership of `callback`,
|
||||
which must be a permanent callback.
|
||||
|
||||
### Using Matchers as Predicates {#MatchersAsPredicatesCheat}
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :---------------------------- | :------------------------------------------ |
|
||||
| `Matches(m)(value)` | evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor. |
|
||||
| `ExplainMatchResult(m, value, result_listener)` | evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`. |
|
||||
| `Value(value, m)` | evaluates to `true` if `value` matches `m`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Defining Matchers
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :----------------------------------- | :------------------------------------ |
|
||||
| `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. |
|
||||
| `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a matcher `IsDivisibleBy(n)` to match a number divisible by `n`. |
|
||||
| `MATCHER_P2(IsBetween, a, b, absl::StrCat(negation ? "isn't" : "is", " between ", PrintToString(a), " and ", PrintToString(b))) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
**Notes:**
|
||||
|
||||
1. The `MATCHER*` macros cannot be used inside a function or class.
|
||||
2. The matcher body must be *purely functional* (i.e. it cannot have any side
|
||||
effect, and the result must not depend on anything other than the value
|
||||
being matched and the matcher parameters).
|
||||
3. You can use `PrintToString(x)` to convert a value `x` of any type to a
|
||||
string.
|
||||
|
||||
## Actions {#ActionList}
|
||||
|
||||
**Actions** specify what a mock function should do when invoked.
|
||||
|
||||
### Returning a Value
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :-------------------------------- | :-------------------------------------------- |
|
||||
| `Return()` | Return from a `void` mock function. |
|
||||
| `Return(value)` | Return `value`. If the type of `value` is different to the mock function's return type, `value` is converted to the latter type <i>at the time the expectation is set</i>, not when the action is executed. |
|
||||
| `ReturnArg<N>()` | Return the `N`-th (0-based) argument. |
|
||||
| `ReturnNew<T>(a1, ..., ak)` | Return `new T(a1, ..., ak)`; a different object is created each time. |
|
||||
| `ReturnNull()` | Return a null pointer. |
|
||||
| `ReturnPointee(ptr)` | Return the value pointed to by `ptr`. |
|
||||
| `ReturnRef(variable)` | Return a reference to `variable`. |
|
||||
| `ReturnRefOfCopy(value)` | Return a reference to a copy of `value`; the copy lives as long as the action. |
|
||||
| `ReturnRoundRobin({a1, ..., ak})` | Each call will return the next `ai` in the list, starting at the beginning when the end of the list is reached. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Side Effects
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :--------------------------------- | :-------------------------------------- |
|
||||
| `Assign(&variable, value)` | Assign `value` to variable. |
|
||||
| `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. |
|
||||
| `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. |
|
||||
| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. |
|
||||
| `SetArgReferee<N>(value)` | Assign `value` to the variable referenced by the `N`-th (0-based) argument. |
|
||||
| `SetArgPointee<N>(value)` | Assign `value` to the variable pointed by the `N`-th (0-based) argument. |
|
||||
| `SetArgumentPointee<N>(value)` | Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0. |
|
||||
| `SetArrayArgument<N>(first, last)` | Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range. |
|
||||
| `SetErrnoAndReturn(error, value)` | Set `errno` to `error` and return `value`. |
|
||||
| `Throw(exception)` | Throws the given exception, which can be any copyable value. Available since v1.1.0. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Using a Function, Functor, or Lambda as an Action
|
||||
|
||||
In the following, by "callable" we mean a free function, `std::function`,
|
||||
functor, or lambda.
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :---------------------------------- | :------------------------------------- |
|
||||
| `f` | Invoke f with the arguments passed to the mock function, where f is a callable. |
|
||||
| `Invoke(f)` | Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor. |
|
||||
| `Invoke(object_pointer, &class::method)` | Invoke the method on the object with the arguments passed to the mock function. |
|
||||
| `InvokeWithoutArgs(f)` | Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments. |
|
||||
| `InvokeWithoutArgs(object_pointer, &class::method)` | Invoke the method on the object, which takes no arguments. |
|
||||
| `InvokeArgument<N>(arg1, arg2, ..., argk)` | Invoke the mock function's `N`-th (0-based) argument, which must be a function or a functor, with the `k` arguments. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
The return value of the invoked function is used as the return value of the
|
||||
action.
|
||||
|
||||
When defining a callable to be used with `Invoke*()`, you can declare any unused
|
||||
parameters as `Unused`:
|
||||
|
||||
```cpp
|
||||
using ::testing::Invoke;
|
||||
double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
|
||||
...
|
||||
EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
|
||||
```
|
||||
|
||||
`Invoke(callback)` and `InvokeWithoutArgs(callback)` take ownership of
|
||||
`callback`, which must be permanent. The type of `callback` must be a base
|
||||
callback type instead of a derived one, e.g.
|
||||
|
||||
```cpp
|
||||
BlockingClosure* done = new BlockingClosure;
|
||||
... Invoke(done) ...; // This won't compile!
|
||||
|
||||
Closure* done2 = new BlockingClosure;
|
||||
... Invoke(done2) ...; // This works.
|
||||
```
|
||||
|
||||
In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference,
|
||||
wrap it inside `std::ref()`. For example,
|
||||
|
||||
```cpp
|
||||
using ::testing::InvokeArgument;
|
||||
...
|
||||
InvokeArgument<2>(5, string("Hi"), std::ref(foo))
|
||||
```
|
||||
|
||||
calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by
|
||||
value, and `foo` by reference.
|
||||
|
||||
### Default Action
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Matcher | Description |
|
||||
| :------------ | :----------------------------------------------------- |
|
||||
| `DoDefault()` | Do the default action (specified by `ON_CALL()` or the built-in one). |
|
||||
<!-- mdformat on -->
|
||||
|
||||
**Note:** due to technical reasons, `DoDefault()` cannot be used inside a
|
||||
composite action - trying to do so will result in a run-time error.
|
||||
|
||||
<!-- GOOGLETEST_CM0032 DO NOT DELETE -->
|
||||
|
||||
### Composite Actions
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :----------------------------- | :------------------------------------------ |
|
||||
| `DoAll(a1, a2, ..., an)` | Do all actions `a1` to `an` and return the result of `an` in each invocation. The first `n - 1` sub-actions must return void and will receive a readonly view of the arguments. |
|
||||
| `IgnoreResult(a)` | Perform action `a` and ignore its result. `a` must not return void. |
|
||||
| `WithArg<N>(a)` | Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it. |
|
||||
| `WithArgs<N1, N2, ..., Nk>(a)` | Pass the selected (0-based) arguments of the mock function to action `a` and perform it. |
|
||||
| `WithoutArgs(a)` | Perform action `a` without any arguments. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
### Defining Actions
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :--------------------------------- | :-------------------------------------- |
|
||||
| `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. |
|
||||
| `ACTION_P(Plus, n) { return arg0 + n; }` | Defines an action `Plus(n)` to return the sum of the mock function's argument #0 and `n`. |
|
||||
| `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
The `ACTION*` macros cannot be used inside a function or class.
|
||||
|
||||
## Cardinalities {#CardinalityList}
|
||||
|
||||
These are used in `Times()` to specify how many times a mock function will be
|
||||
called:
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| | |
|
||||
| :---------------- | :----------------------------------------------------- |
|
||||
| `AnyNumber()` | The function can be called any number of times. |
|
||||
| `AtLeast(n)` | The call is expected at least `n` times. |
|
||||
| `AtMost(n)` | The call is expected at most `n` times. |
|
||||
| `Between(m, n)` | The call is expected between `m` and `n` (inclusive) times. |
|
||||
| `Exactly(n) or n` | The call is expected exactly `n` times. In particular, the call should never happen when `n` is 0. |
|
||||
<!-- mdformat on -->
|
||||
|
||||
## Expectation Order
|
||||
|
||||
By default, the expectations can be matched in *any* order. If some or all
|
||||
expectations must be matched in a given order, there are two ways to specify it.
|
||||
They can be used either independently or together.
|
||||
|
||||
### The After Clause {#AfterClause}
|
||||
|
||||
```cpp
|
||||
using ::testing::Expectation;
|
||||
...
|
||||
Expectation init_x = EXPECT_CALL(foo, InitX());
|
||||
Expectation init_y = EXPECT_CALL(foo, InitY());
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.After(init_x, init_y);
|
||||
```
|
||||
|
||||
says that `Bar()` can be called only after both `InitX()` and `InitY()` have
|
||||
been called.
|
||||
|
||||
If you don't know how many pre-requisites an expectation has when you write it,
|
||||
you can use an `ExpectationSet` to collect them:
|
||||
|
||||
```cpp
|
||||
using ::testing::ExpectationSet;
|
||||
...
|
||||
ExpectationSet all_inits;
|
||||
for (int i = 0; i < element_count; i++) {
|
||||
all_inits += EXPECT_CALL(foo, InitElement(i));
|
||||
}
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.After(all_inits);
|
||||
```
|
||||
|
||||
says that `Bar()` can be called only after all elements have been initialized
|
||||
(but we don't care about which elements get initialized before the others).
|
||||
|
||||
Modifying an `ExpectationSet` after using it in an `.After()` doesn't affect the
|
||||
meaning of the `.After()`.
|
||||
|
||||
### Sequences {#UsingSequences}
|
||||
|
||||
When you have a long chain of sequential expectations, it's easier to specify
|
||||
the order using **sequences**, which don't require you to given each expectation
|
||||
in the chain a different name. *All expected calls* in the same sequence must
|
||||
occur in the order they are specified.
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
using ::testing::Sequence;
|
||||
Sequence s1, s2;
|
||||
...
|
||||
EXPECT_CALL(foo, Reset())
|
||||
.InSequence(s1, s2)
|
||||
.WillOnce(Return(true));
|
||||
EXPECT_CALL(foo, GetSize())
|
||||
.InSequence(s1)
|
||||
.WillOnce(Return(1));
|
||||
EXPECT_CALL(foo, Describe(A<const char*>()))
|
||||
.InSequence(s2)
|
||||
.WillOnce(Return("dummy"));
|
||||
```
|
||||
|
||||
says that `Reset()` must be called before *both* `GetSize()` *and* `Describe()`,
|
||||
and the latter two can occur in any order.
|
||||
|
||||
To put many expectations in a sequence conveniently:
|
||||
|
||||
```cpp
|
||||
using ::testing::InSequence;
|
||||
{
|
||||
InSequence seq;
|
||||
|
||||
EXPECT_CALL(...)...;
|
||||
EXPECT_CALL(...)...;
|
||||
...
|
||||
EXPECT_CALL(...)...;
|
||||
}
|
||||
```
|
||||
|
||||
says that all expected calls in the scope of `seq` must occur in strict order.
|
||||
The name `seq` is irrelevant.
|
||||
|
||||
## Verifying and Resetting a Mock
|
||||
|
||||
gMock will verify the expectations on a mock object when it is destructed, or
|
||||
you can do it earlier:
|
||||
|
||||
```cpp
|
||||
using ::testing::Mock;
|
||||
...
|
||||
// Verifies and removes the expectations on mock_obj;
|
||||
// returns true if and only if successful.
|
||||
Mock::VerifyAndClearExpectations(&mock_obj);
|
||||
...
|
||||
// Verifies and removes the expectations on mock_obj;
|
||||
// also removes the default actions set by ON_CALL();
|
||||
// returns true if and only if successful.
|
||||
Mock::VerifyAndClear(&mock_obj);
|
||||
```
|
||||
|
||||
You can also tell gMock that a mock object can be leaked and doesn't need to be
|
||||
verified:
|
||||
|
||||
```cpp
|
||||
Mock::AllowLeak(&mock_obj);
|
||||
```
|
||||
|
||||
## Mock Classes
|
||||
|
||||
gMock defines a convenient mock class template
|
||||
|
||||
```cpp
|
||||
class MockFunction<R(A1, ..., An)> {
|
||||
public:
|
||||
MOCK_METHOD(R, Call, (A1, ..., An));
|
||||
};
|
||||
```
|
||||
|
||||
See this [recipe](gmock_cook_book.md#using-check-points) for one application of it.
|
||||
|
||||
## Flags
|
||||
|
||||
<!-- mdformat off(no multiline tables) -->
|
||||
| Flag | Description |
|
||||
| :----------------------------- | :---------------------------------------- |
|
||||
| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
|
||||
| `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |
|
||||
<!-- mdformat on -->
|
||||
4267
docs/gmock_cook_book.md
Normal file
4267
docs/gmock_cook_book.md
Normal file
File diff suppressed because it is too large
Load Diff
398
docs/gmock_faq.md
Normal file
398
docs/gmock_faq.md
Normal file
@@ -0,0 +1,398 @@
|
||||
## Legacy gMock FAQ {#GMockFaq}
|
||||
|
||||
<!-- GOOGLETEST_CM0021 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
### When I call a method on my mock object, the method for the real object is invoked instead. What's the problem?
|
||||
|
||||
In order for a method to be mocked, it must be *virtual*, unless you use the
|
||||
[high-perf dependency injection technique](gmock_cook_book.md#MockingNonVirtualMethods).
|
||||
|
||||
### Can I mock a variadic function?
|
||||
|
||||
You cannot mock a variadic function (i.e. a function taking ellipsis (`...`)
|
||||
arguments) directly in gMock.
|
||||
|
||||
The problem is that in general, there is *no way* for a mock object to know how
|
||||
many arguments are passed to the variadic method, and what the arguments' types
|
||||
are. Only the *author of the base class* knows the protocol, and we cannot look
|
||||
into his or her head.
|
||||
|
||||
Therefore, to mock such a function, the *user* must teach the mock object how to
|
||||
figure out the number of arguments and their types. One way to do it is to
|
||||
provide overloaded versions of the function.
|
||||
|
||||
Ellipsis arguments are inherited from C and not really a C++ feature. They are
|
||||
unsafe to use and don't work with arguments that have constructors or
|
||||
destructors. Therefore we recommend to avoid them in C++ as much as possible.
|
||||
|
||||
### MSVC gives me warning C4301 or C4373 when I define a mock method with a const parameter. Why?
|
||||
|
||||
If you compile this using Microsoft Visual C++ 2005 SP1:
|
||||
|
||||
```cpp
|
||||
class Foo {
|
||||
...
|
||||
virtual void Bar(const int i) = 0;
|
||||
};
|
||||
|
||||
class MockFoo : public Foo {
|
||||
...
|
||||
MOCK_METHOD(void, Bar, (const int i), (override));
|
||||
};
|
||||
```
|
||||
|
||||
You may get the following warning:
|
||||
|
||||
```shell
|
||||
warning C4301: 'MockFoo::Bar': overriding virtual function only differs from 'Foo::Bar' by const/volatile qualifier
|
||||
```
|
||||
|
||||
This is a MSVC bug. The same code compiles fine with gcc, for example. If you
|
||||
use Visual C++ 2008 SP1, you would get the warning:
|
||||
|
||||
```shell
|
||||
warning C4373: 'MockFoo::Bar': virtual function overrides 'Foo::Bar', previous versions of the compiler did not override when parameters only differed by const/volatile qualifiers
|
||||
```
|
||||
|
||||
In C++, if you *declare* a function with a `const` parameter, the `const`
|
||||
modifier is ignored. Therefore, the `Foo` base class above is equivalent to:
|
||||
|
||||
```cpp
|
||||
class Foo {
|
||||
...
|
||||
virtual void Bar(int i) = 0; // int or const int? Makes no difference.
|
||||
};
|
||||
```
|
||||
|
||||
In fact, you can *declare* `Bar()` with an `int` parameter, and define it with a
|
||||
`const int` parameter. The compiler will still match them up.
|
||||
|
||||
Since making a parameter `const` is meaningless in the method declaration, we
|
||||
recommend to remove it in both `Foo` and `MockFoo`. That should workaround the
|
||||
VC bug.
|
||||
|
||||
Note that we are talking about the *top-level* `const` modifier here. If the
|
||||
function parameter is passed by pointer or reference, declaring the pointee or
|
||||
referee as `const` is still meaningful. For example, the following two
|
||||
declarations are *not* equivalent:
|
||||
|
||||
```cpp
|
||||
void Bar(int* p); // Neither p nor *p is const.
|
||||
void Bar(const int* p); // p is not const, but *p is.
|
||||
```
|
||||
|
||||
<!-- GOOGLETEST_CM0030 DO NOT DELETE -->
|
||||
|
||||
### I can't figure out why gMock thinks my expectations are not satisfied. What should I do?
|
||||
|
||||
You might want to run your test with `--gmock_verbose=info`. This flag lets
|
||||
gMock print a trace of every mock function call it receives. By studying the
|
||||
trace, you'll gain insights on why the expectations you set are not met.
|
||||
|
||||
If you see the message "The mock function has no default action set, and its
|
||||
return type has no default value set.", then try
|
||||
[adding a default action](gmock_for_dummies.md#DefaultValue). Due to a known
|
||||
issue, unexpected calls on mocks without default actions don't print out a
|
||||
detailed comparison between the actual arguments and the expected arguments.
|
||||
|
||||
### My program crashed and `ScopedMockLog` spit out tons of messages. Is it a gMock bug?
|
||||
|
||||
gMock and `ScopedMockLog` are likely doing the right thing here.
|
||||
|
||||
When a test crashes, the failure signal handler will try to log a lot of
|
||||
information (the stack trace, and the address map, for example). The messages
|
||||
are compounded if you have many threads with depth stacks. When `ScopedMockLog`
|
||||
intercepts these messages and finds that they don't match any expectations, it
|
||||
prints an error for each of them.
|
||||
|
||||
You can learn to ignore the errors, or you can rewrite your expectations to make
|
||||
your test more robust, for example, by adding something like:
|
||||
|
||||
```cpp
|
||||
using ::testing::AnyNumber;
|
||||
using ::testing::Not;
|
||||
...
|
||||
// Ignores any log not done by us.
|
||||
EXPECT_CALL(log, Log(_, Not(EndsWith("/my_file.cc")), _))
|
||||
.Times(AnyNumber());
|
||||
```
|
||||
|
||||
### How can I assert that a function is NEVER called?
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
EXPECT_CALL(foo, Bar(_))
|
||||
.Times(0);
|
||||
```
|
||||
|
||||
<!-- GOOGLETEST_CM0031 DO NOT DELETE -->
|
||||
|
||||
### I have a failed test where gMock tells me TWICE that a particular expectation is not satisfied. Isn't this redundant?
|
||||
|
||||
When gMock detects a failure, it prints relevant information (the mock function
|
||||
arguments, the state of relevant expectations, and etc) to help the user debug.
|
||||
If another failure is detected, gMock will do the same, including printing the
|
||||
state of relevant expectations.
|
||||
|
||||
Sometimes an expectation's state didn't change between two failures, and you'll
|
||||
see the same description of the state twice. They are however *not* redundant,
|
||||
as they refer to *different points in time*. The fact they are the same *is*
|
||||
interesting information.
|
||||
|
||||
### I get a heapcheck failure when using a mock object, but using a real object is fine. What can be wrong?
|
||||
|
||||
Does the class (hopefully a pure interface) you are mocking have a virtual
|
||||
destructor?
|
||||
|
||||
Whenever you derive from a base class, make sure its destructor is virtual.
|
||||
Otherwise Bad Things will happen. Consider the following code:
|
||||
|
||||
```cpp
|
||||
class Base {
|
||||
public:
|
||||
// Not virtual, but should be.
|
||||
~Base() { ... }
|
||||
...
|
||||
};
|
||||
|
||||
class Derived : public Base {
|
||||
public:
|
||||
...
|
||||
private:
|
||||
std::string value_;
|
||||
};
|
||||
|
||||
...
|
||||
Base* p = new Derived;
|
||||
...
|
||||
delete p; // Surprise! ~Base() will be called, but ~Derived() will not
|
||||
// - value_ is leaked.
|
||||
```
|
||||
|
||||
By changing `~Base()` to virtual, `~Derived()` will be correctly called when
|
||||
`delete p` is executed, and the heap checker will be happy.
|
||||
|
||||
### The "newer expectations override older ones" rule makes writing expectations awkward. Why does gMock do that?
|
||||
|
||||
When people complain about this, often they are referring to code like:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
// foo.Bar() should be called twice, return 1 the first time, and return
|
||||
// 2 the second time. However, I have to write the expectations in the
|
||||
// reverse order. This sucks big time!!!
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.WillOnce(Return(2))
|
||||
.RetiresOnSaturation();
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.WillOnce(Return(1))
|
||||
.RetiresOnSaturation();
|
||||
```
|
||||
|
||||
The problem, is that they didn't pick the **best** way to express the test's
|
||||
intent.
|
||||
|
||||
By default, expectations don't have to be matched in *any* particular order. If
|
||||
you want them to match in a certain order, you need to be explicit. This is
|
||||
gMock's (and jMock's) fundamental philosophy: it's easy to accidentally
|
||||
over-specify your tests, and we want to make it harder to do so.
|
||||
|
||||
There are two better ways to write the test spec. You could either put the
|
||||
expectations in sequence:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
// foo.Bar() should be called twice, return 1 the first time, and return
|
||||
// 2 the second time. Using a sequence, we can write the expectations
|
||||
// in their natural order.
|
||||
{
|
||||
InSequence s;
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.WillOnce(Return(1))
|
||||
.RetiresOnSaturation();
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.WillOnce(Return(2))
|
||||
.RetiresOnSaturation();
|
||||
}
|
||||
```
|
||||
|
||||
or you can put the sequence of actions in the same expectation:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
// foo.Bar() should be called twice, return 1 the first time, and return
|
||||
// 2 the second time.
|
||||
EXPECT_CALL(foo, Bar())
|
||||
.WillOnce(Return(1))
|
||||
.WillOnce(Return(2))
|
||||
.RetiresOnSaturation();
|
||||
```
|
||||
|
||||
Back to the original questions: why does gMock search the expectations (and
|
||||
`ON_CALL`s) from back to front? Because this allows a user to set up a mock's
|
||||
behavior for the common case early (e.g. in the mock's constructor or the test
|
||||
fixture's set-up phase) and customize it with more specific rules later. If
|
||||
gMock searches from front to back, this very useful pattern won't be possible.
|
||||
|
||||
### gMock prints a warning when a function without EXPECT_CALL is called, even if I have set its behavior using ON_CALL. Would it be reasonable not to show the warning in this case?
|
||||
|
||||
When choosing between being neat and being safe, we lean toward the latter. So
|
||||
the answer is that we think it's better to show the warning.
|
||||
|
||||
Often people write `ON_CALL`s in the mock object's constructor or `SetUp()`, as
|
||||
the default behavior rarely changes from test to test. Then in the test body
|
||||
they set the expectations, which are often different for each test. Having an
|
||||
`ON_CALL` in the set-up part of a test doesn't mean that the calls are expected.
|
||||
If there's no `EXPECT_CALL` and the method is called, it's possibly an error. If
|
||||
we quietly let the call go through without notifying the user, bugs may creep in
|
||||
unnoticed.
|
||||
|
||||
If, however, you are sure that the calls are OK, you can write
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
EXPECT_CALL(foo, Bar(_))
|
||||
.WillRepeatedly(...);
|
||||
```
|
||||
|
||||
instead of
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
ON_CALL(foo, Bar(_))
|
||||
.WillByDefault(...);
|
||||
```
|
||||
|
||||
This tells gMock that you do expect the calls and no warning should be printed.
|
||||
|
||||
Also, you can control the verbosity by specifying `--gmock_verbose=error`. Other
|
||||
values are `info` and `warning`. If you find the output too noisy when
|
||||
debugging, just choose a less verbose level.
|
||||
|
||||
### How can I delete the mock function's argument in an action?
|
||||
|
||||
If your mock function takes a pointer argument and you want to delete that
|
||||
argument, you can use testing::DeleteArg<N>() to delete the N'th (zero-indexed)
|
||||
argument:
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
MOCK_METHOD(void, Bar, (X* x, const Y& y));
|
||||
...
|
||||
EXPECT_CALL(mock_foo_, Bar(_, _))
|
||||
.WillOnce(testing::DeleteArg<0>()));
|
||||
```
|
||||
|
||||
### How can I perform an arbitrary action on a mock function's argument?
|
||||
|
||||
If you find yourself needing to perform some action that's not supported by
|
||||
gMock directly, remember that you can define your own actions using
|
||||
[`MakeAction()`](#NewMonoActions) or
|
||||
[`MakePolymorphicAction()`](#NewPolyActions), or you can write a stub function
|
||||
and invoke it using [`Invoke()`](#FunctionsAsActions).
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
using ::testing::Invoke;
|
||||
...
|
||||
MOCK_METHOD(void, Bar, (X* p));
|
||||
...
|
||||
EXPECT_CALL(mock_foo_, Bar(_))
|
||||
.WillOnce(Invoke(MyAction(...)));
|
||||
```
|
||||
|
||||
### My code calls a static/global function. Can I mock it?
|
||||
|
||||
You can, but you need to make some changes.
|
||||
|
||||
In general, if you find yourself needing to mock a static function, it's a sign
|
||||
that your modules are too tightly coupled (and less flexible, less reusable,
|
||||
less testable, etc). You are probably better off defining a small interface and
|
||||
call the function through that interface, which then can be easily mocked. It's
|
||||
a bit of work initially, but usually pays for itself quickly.
|
||||
|
||||
This Google Testing Blog
|
||||
[post](https://testing.googleblog.com/2008/06/defeat-static-cling.html) says it
|
||||
excellently. Check it out.
|
||||
|
||||
### My mock object needs to do complex stuff. It's a lot of pain to specify the actions. gMock sucks!
|
||||
|
||||
I know it's not a question, but you get an answer for free any way. :-)
|
||||
|
||||
With gMock, you can create mocks in C++ easily. And people might be tempted to
|
||||
use them everywhere. Sometimes they work great, and sometimes you may find them,
|
||||
well, a pain to use. So, what's wrong in the latter case?
|
||||
|
||||
When you write a test without using mocks, you exercise the code and assert that
|
||||
it returns the correct value or that the system is in an expected state. This is
|
||||
sometimes called "state-based testing".
|
||||
|
||||
Mocks are great for what some call "interaction-based" testing: instead of
|
||||
checking the system state at the very end, mock objects verify that they are
|
||||
invoked the right way and report an error as soon as it arises, giving you a
|
||||
handle on the precise context in which the error was triggered. This is often
|
||||
more effective and economical to do than state-based testing.
|
||||
|
||||
If you are doing state-based testing and using a test double just to simulate
|
||||
the real object, you are probably better off using a fake. Using a mock in this
|
||||
case causes pain, as it's not a strong point for mocks to perform complex
|
||||
actions. If you experience this and think that mocks suck, you are just not
|
||||
using the right tool for your problem. Or, you might be trying to solve the
|
||||
wrong problem. :-)
|
||||
|
||||
### I got a warning "Uninteresting function call encountered - default action taken.." Should I panic?
|
||||
|
||||
By all means, NO! It's just an FYI. :-)
|
||||
|
||||
What it means is that you have a mock function, you haven't set any expectations
|
||||
on it (by gMock's rule this means that you are not interested in calls to this
|
||||
function and therefore it can be called any number of times), and it is called.
|
||||
That's OK - you didn't say it's not OK to call the function!
|
||||
|
||||
What if you actually meant to disallow this function to be called, but forgot to
|
||||
write `EXPECT_CALL(foo, Bar()).Times(0)`? While one can argue that it's the
|
||||
user's fault, gMock tries to be nice and prints you a note.
|
||||
|
||||
So, when you see the message and believe that there shouldn't be any
|
||||
uninteresting calls, you should investigate what's going on. To make your life
|
||||
easier, gMock dumps the stack trace when an uninteresting call is encountered.
|
||||
From that you can figure out which mock function it is, and how it is called.
|
||||
|
||||
### I want to define a custom action. Should I use Invoke() or implement the ActionInterface interface?
|
||||
|
||||
Either way is fine - you want to choose the one that's more convenient for your
|
||||
circumstance.
|
||||
|
||||
Usually, if your action is for a particular function type, defining it using
|
||||
`Invoke()` should be easier; if your action can be used in functions of
|
||||
different types (e.g. if you are defining `Return(*value*)`),
|
||||
`MakePolymorphicAction()` is easiest. Sometimes you want precise control on what
|
||||
types of functions the action can be used in, and implementing `ActionInterface`
|
||||
is the way to go here. See the implementation of `Return()` in
|
||||
`testing/base/public/gmock-actions.h` for an example.
|
||||
|
||||
### I use SetArgPointee() in WillOnce(), but gcc complains about "conflicting return type specified". What does it mean?
|
||||
|
||||
You got this error as gMock has no idea what value it should return when the
|
||||
mock method is called. `SetArgPointee()` says what the side effect is, but
|
||||
doesn't say what the return value should be. You need `DoAll()` to chain a
|
||||
`SetArgPointee()` with a `Return()` that provides a value appropriate to the API
|
||||
being mocked.
|
||||
|
||||
See this [recipe](gmock_cook_book.md#mocking-side-effects) for more details and
|
||||
an example.
|
||||
|
||||
### I have a huge mock class, and Microsoft Visual C++ runs out of memory when compiling it. What can I do?
|
||||
|
||||
We've noticed that when the `/clr` compiler flag is used, Visual C++ uses 5~6
|
||||
times as much memory when compiling a mock class. We suggest to avoid `/clr`
|
||||
when compiling native C++ mocks.
|
||||
702
docs/gmock_for_dummies.md
Normal file
702
docs/gmock_for_dummies.md
Normal file
@@ -0,0 +1,702 @@
|
||||
# gMock for Dummies {#GMockForDummies}
|
||||
|
||||
<!-- GOOGLETEST_CM0013 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
## What Is gMock?
|
||||
|
||||
When you write a prototype or test, often it's not feasible or wise to rely on
|
||||
real objects entirely. A **mock object** implements the same interface as a real
|
||||
object (so it can be used as one), but lets you specify at run time how it will
|
||||
be used and what it should do (which methods will be called? in which order? how
|
||||
many times? with what arguments? what will they return? etc).
|
||||
|
||||
**Note:** It is easy to confuse the term *fake objects* with mock objects. Fakes
|
||||
and mocks actually mean very different things in the Test-Driven Development
|
||||
(TDD) community:
|
||||
|
||||
* **Fake** objects have working implementations, but usually take some
|
||||
shortcut (perhaps to make the operations less expensive), which makes them
|
||||
not suitable for production. An in-memory file system would be an example of
|
||||
a fake.
|
||||
* **Mocks** are objects pre-programmed with *expectations*, which form a
|
||||
specification of the calls they are expected to receive.
|
||||
|
||||
If all this seems too abstract for you, don't worry - the most important thing
|
||||
to remember is that a mock allows you to check the *interaction* between itself
|
||||
and code that uses it. The difference between fakes and mocks shall become much
|
||||
clearer once you start to use mocks.
|
||||
|
||||
**gMock** is a library (sometimes we also call it a "framework" to make it sound
|
||||
cool) for creating mock classes and using them. It does to C++ what
|
||||
jMock/EasyMock does to Java (well, more or less).
|
||||
|
||||
When using gMock,
|
||||
|
||||
1. first, you use some simple macros to describe the interface you want to
|
||||
mock, and they will expand to the implementation of your mock class;
|
||||
2. next, you create some mock objects and specify its expectations and behavior
|
||||
using an intuitive syntax;
|
||||
3. then you exercise code that uses the mock objects. gMock will catch any
|
||||
violation to the expectations as soon as it arises.
|
||||
|
||||
## Why gMock?
|
||||
|
||||
While mock objects help you remove unnecessary dependencies in tests and make
|
||||
them fast and reliable, using mocks manually in C++ is *hard*:
|
||||
|
||||
* Someone has to implement the mocks. The job is usually tedious and
|
||||
error-prone. No wonder people go great distance to avoid it.
|
||||
* The quality of those manually written mocks is a bit, uh, unpredictable. You
|
||||
may see some really polished ones, but you may also see some that were
|
||||
hacked up in a hurry and have all sorts of ad hoc restrictions.
|
||||
* The knowledge you gained from using one mock doesn't transfer to the next
|
||||
one.
|
||||
|
||||
In contrast, Java and Python programmers have some fine mock frameworks (jMock,
|
||||
EasyMock, [Mox](http://wtf/mox), etc), which automate the creation of mocks. As
|
||||
a result, mocking is a proven effective technique and widely adopted practice in
|
||||
those communities. Having the right tool absolutely makes the difference.
|
||||
|
||||
gMock was built to help C++ programmers. It was inspired by jMock and EasyMock,
|
||||
but designed with C++'s specifics in mind. It is your friend if any of the
|
||||
following problems is bothering you:
|
||||
|
||||
* You are stuck with a sub-optimal design and wish you had done more
|
||||
prototyping before it was too late, but prototyping in C++ is by no means
|
||||
"rapid".
|
||||
* Your tests are slow as they depend on too many libraries or use expensive
|
||||
resources (e.g. a database).
|
||||
* Your tests are brittle as some resources they use are unreliable (e.g. the
|
||||
network).
|
||||
* You want to test how your code handles a failure (e.g. a file checksum
|
||||
error), but it's not easy to cause one.
|
||||
* You need to make sure that your module interacts with other modules in the
|
||||
right way, but it's hard to observe the interaction; therefore you resort to
|
||||
observing the side effects at the end of the action, but it's awkward at
|
||||
best.
|
||||
* You want to "mock out" your dependencies, except that they don't have mock
|
||||
implementations yet; and, frankly, you aren't thrilled by some of those
|
||||
hand-written mocks.
|
||||
|
||||
We encourage you to use gMock as
|
||||
|
||||
* a *design* tool, for it lets you experiment with your interface design early
|
||||
and often. More iterations lead to better designs!
|
||||
* a *testing* tool to cut your tests' outbound dependencies and probe the
|
||||
interaction between your module and its collaborators.
|
||||
|
||||
## Getting Started
|
||||
|
||||
gMock is bundled with googletest.
|
||||
|
||||
## A Case for Mock Turtles
|
||||
|
||||
Let's look at an example. Suppose you are developing a graphics program that
|
||||
relies on a [LOGO](http://en.wikipedia.org/wiki/Logo_programming_language)-like
|
||||
API for drawing. How would you test that it does the right thing? Well, you can
|
||||
run it and compare the screen with a golden screen snapshot, but let's admit it:
|
||||
tests like this are expensive to run and fragile (What if you just upgraded to a
|
||||
shiny new graphics card that has better anti-aliasing? Suddenly you have to
|
||||
update all your golden images.). It would be too painful if all your tests are
|
||||
like this. Fortunately, you learned about
|
||||
[Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection) and know the right thing
|
||||
to do: instead of having your application talk to the system API directly, wrap
|
||||
the API in an interface (say, `Turtle`) and code to that interface:
|
||||
|
||||
```cpp
|
||||
class Turtle {
|
||||
...
|
||||
virtual ~Turtle() {}
|
||||
virtual void PenUp() = 0;
|
||||
virtual void PenDown() = 0;
|
||||
virtual void Forward(int distance) = 0;
|
||||
virtual void Turn(int degrees) = 0;
|
||||
virtual void GoTo(int x, int y) = 0;
|
||||
virtual int GetX() const = 0;
|
||||
virtual int GetY() const = 0;
|
||||
};
|
||||
```
|
||||
|
||||
(Note that the destructor of `Turtle` **must** be virtual, as is the case for
|
||||
**all** classes you intend to inherit from - otherwise the destructor of the
|
||||
derived class will not be called when you delete an object through a base
|
||||
pointer, and you'll get corrupted program states like memory leaks.)
|
||||
|
||||
You can control whether the turtle's movement will leave a trace using `PenUp()`
|
||||
and `PenDown()`, and control its movement using `Forward()`, `Turn()`, and
|
||||
`GoTo()`. Finally, `GetX()` and `GetY()` tell you the current position of the
|
||||
turtle.
|
||||
|
||||
Your program will normally use a real implementation of this interface. In
|
||||
tests, you can use a mock implementation instead. This allows you to easily
|
||||
check what drawing primitives your program is calling, with what arguments, and
|
||||
in which order. Tests written this way are much more robust (they won't break
|
||||
because your new machine does anti-aliasing differently), easier to read and
|
||||
maintain (the intent of a test is expressed in the code, not in some binary
|
||||
images), and run *much, much faster*.
|
||||
|
||||
## Writing the Mock Class
|
||||
|
||||
If you are lucky, the mocks you need to use have already been implemented by
|
||||
some nice people. If, however, you find yourself in the position to write a mock
|
||||
class, relax - gMock turns this task into a fun game! (Well, almost.)
|
||||
|
||||
### How to Define It
|
||||
|
||||
Using the `Turtle` interface as example, here are the simple steps you need to
|
||||
follow:
|
||||
|
||||
* Derive a class `MockTurtle` from `Turtle`.
|
||||
* Take a *virtual* function of `Turtle` (while it's possible to
|
||||
[mock non-virtual methods using templates](gmock_cook_book.md#MockingNonVirtualMethods),
|
||||
it's much more involved).
|
||||
* In the `public:` section of the child class, write `MOCK_METHOD();`
|
||||
* Now comes the fun part: you take the function signature, cut-and-paste it
|
||||
into the macro, and add two commas - one between the return type and the
|
||||
name, another between the name and the argument list.
|
||||
* If you're mocking a const method, add a 4th parameter containing `(const)`
|
||||
(the parentheses are required).
|
||||
* Since you're overriding a virtual method, we suggest adding the `override`
|
||||
keyword. For const methods the 4th parameter becomes `(const, override)`,
|
||||
for non-const methods just `(override)`. This isn't mandatory.
|
||||
* Repeat until all virtual functions you want to mock are done. (It goes
|
||||
without saying that *all* pure virtual methods in your abstract class must
|
||||
be either mocked or overridden.)
|
||||
|
||||
After the process, you should have something like:
|
||||
|
||||
```cpp
|
||||
#include "gmock/gmock.h" // Brings in gMock.
|
||||
|
||||
class MockTurtle : public Turtle {
|
||||
public:
|
||||
...
|
||||
MOCK_METHOD(void, PenUp, (), (override));
|
||||
MOCK_METHOD(void, PenDown, (), (override));
|
||||
MOCK_METHOD(void, Forward, (int distance), (override));
|
||||
MOCK_METHOD(void, Turn, (int degrees), (override));
|
||||
MOCK_METHOD(void, GoTo, (int x, int y), (override));
|
||||
MOCK_METHOD(int, GetX, (), (const, override));
|
||||
MOCK_METHOD(int, GetY, (), (const, override));
|
||||
};
|
||||
```
|
||||
|
||||
You don't need to define these mock methods somewhere else - the `MOCK_METHOD`
|
||||
macro will generate the definitions for you. It's that simple!
|
||||
|
||||
### Where to Put It
|
||||
|
||||
When you define a mock class, you need to decide where to put its definition.
|
||||
Some people put it in a `_test.cc`. This is fine when the interface being mocked
|
||||
(say, `Foo`) is owned by the same person or team. Otherwise, when the owner of
|
||||
`Foo` changes it, your test could break. (You can't really expect `Foo`'s
|
||||
maintainer to fix every test that uses `Foo`, can you?)
|
||||
|
||||
So, the rule of thumb is: if you need to mock `Foo` and it's owned by others,
|
||||
define the mock class in `Foo`'s package (better, in a `testing` sub-package
|
||||
such that you can clearly separate production code and testing utilities), put
|
||||
it in a `.h` and a `cc_library`. Then everyone can reference them from their
|
||||
tests. If `Foo` ever changes, there is only one copy of `MockFoo` to change, and
|
||||
only tests that depend on the changed methods need to be fixed.
|
||||
|
||||
Another way to do it: you can introduce a thin layer `FooAdaptor` on top of
|
||||
`Foo` and code to this new interface. Since you own `FooAdaptor`, you can absorb
|
||||
changes in `Foo` much more easily. While this is more work initially, carefully
|
||||
choosing the adaptor interface can make your code easier to write and more
|
||||
readable (a net win in the long run), as you can choose `FooAdaptor` to fit your
|
||||
specific domain much better than `Foo` does.
|
||||
|
||||
<!-- GOOGLETEST_CM0029 DO NOT DELETE -->
|
||||
|
||||
## Using Mocks in Tests
|
||||
|
||||
Once you have a mock class, using it is easy. The typical work flow is:
|
||||
|
||||
1. Import the gMock names from the `testing` namespace such that you can use
|
||||
them unqualified (You only have to do it once per file). Remember that
|
||||
namespaces are a good idea.
|
||||
2. Create some mock objects.
|
||||
3. Specify your expectations on them (How many times will a method be called?
|
||||
With what arguments? What should it do? etc.).
|
||||
4. Exercise some code that uses the mocks; optionally, check the result using
|
||||
googletest assertions. If a mock method is called more than expected or with
|
||||
wrong arguments, you'll get an error immediately.
|
||||
5. When a mock is destructed, gMock will automatically check whether all
|
||||
expectations on it have been satisfied.
|
||||
|
||||
Here's an example:
|
||||
|
||||
```cpp
|
||||
#include "path/to/mock-turtle.h"
|
||||
#include "gmock/gmock.h"
|
||||
#include "gtest/gtest.h"
|
||||
|
||||
using ::testing::AtLeast; // #1
|
||||
|
||||
TEST(PainterTest, CanDrawSomething) {
|
||||
MockTurtle turtle; // #2
|
||||
EXPECT_CALL(turtle, PenDown()) // #3
|
||||
.Times(AtLeast(1));
|
||||
|
||||
Painter painter(&turtle); // #4
|
||||
|
||||
EXPECT_TRUE(painter.DrawCircle(0, 0, 10)); // #5
|
||||
}
|
||||
```
|
||||
|
||||
As you might have guessed, this test checks that `PenDown()` is called at least
|
||||
once. If the `painter` object didn't call this method, your test will fail with
|
||||
a message like this:
|
||||
|
||||
```text
|
||||
path/to/my_test.cc:119: Failure
|
||||
Actual function call count doesn't match this expectation:
|
||||
Actually: never called;
|
||||
Expected: called at least once.
|
||||
Stack trace:
|
||||
...
|
||||
```
|
||||
|
||||
**Tip 1:** If you run the test from an Emacs buffer, you can hit `<Enter>` on
|
||||
the line number to jump right to the failed expectation.
|
||||
|
||||
**Tip 2:** If your mock objects are never deleted, the final verification won't
|
||||
happen. Therefore it's a good idea to turn on the heap checker in your tests
|
||||
when you allocate mocks on the heap. You get that automatically if you use the
|
||||
`gtest_main` library already.
|
||||
|
||||
**Important note:** gMock requires expectations to be set **before** the mock
|
||||
functions are called, otherwise the behavior is **undefined**. In particular,
|
||||
you mustn't interleave `EXPECT_CALL()s` and calls to the mock functions.
|
||||
|
||||
This means `EXPECT_CALL()` should be read as expecting that a call will occur
|
||||
*in the future*, not that a call has occurred. Why does gMock work like that?
|
||||
Well, specifying the expectation beforehand allows gMock to report a violation
|
||||
as soon as it rises, when the context (stack trace, etc) is still available.
|
||||
This makes debugging much easier.
|
||||
|
||||
Admittedly, this test is contrived and doesn't do much. You can easily achieve
|
||||
the same effect without using gMock. However, as we shall reveal soon, gMock
|
||||
allows you to do *so much more* with the mocks.
|
||||
|
||||
## Setting Expectations
|
||||
|
||||
The key to using a mock object successfully is to set the *right expectations*
|
||||
on it. If you set the expectations too strict, your test will fail as the result
|
||||
of unrelated changes. If you set them too loose, bugs can slip through. You want
|
||||
to do it just right such that your test can catch exactly the kind of bugs you
|
||||
intend it to catch. gMock provides the necessary means for you to do it "just
|
||||
right."
|
||||
|
||||
### General Syntax
|
||||
|
||||
In gMock we use the `EXPECT_CALL()` macro to set an expectation on a mock
|
||||
method. The general syntax is:
|
||||
|
||||
```cpp
|
||||
EXPECT_CALL(mock_object, method(matchers))
|
||||
.Times(cardinality)
|
||||
.WillOnce(action)
|
||||
.WillRepeatedly(action);
|
||||
```
|
||||
|
||||
The macro has two arguments: first the mock object, and then the method and its
|
||||
arguments. Note that the two are separated by a comma (`,`), not a period (`.`).
|
||||
(Why using a comma? The answer is that it was necessary for technical reasons.)
|
||||
If the method is not overloaded, the macro can also be called without matchers:
|
||||
|
||||
```cpp
|
||||
EXPECT_CALL(mock_object, non-overloaded-method)
|
||||
.Times(cardinality)
|
||||
.WillOnce(action)
|
||||
.WillRepeatedly(action);
|
||||
```
|
||||
|
||||
This syntax allows the test writer to specify "called with any arguments"
|
||||
without explicitly specifying the number or types of arguments. To avoid
|
||||
unintended ambiguity, this syntax may only be used for methods which are not
|
||||
overloaded
|
||||
|
||||
Either form of the macro can be followed by some optional *clauses* that provide
|
||||
more information about the expectation. We'll discuss how each clause works in
|
||||
the coming sections.
|
||||
|
||||
This syntax is designed to make an expectation read like English. For example,
|
||||
you can probably guess that
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.Times(5)
|
||||
.WillOnce(Return(100))
|
||||
.WillOnce(Return(150))
|
||||
.WillRepeatedly(Return(200));
|
||||
```
|
||||
|
||||
says that the `turtle` object's `GetX()` method will be called five times, it
|
||||
will return 100 the first time, 150 the second time, and then 200 every time.
|
||||
Some people like to call this style of syntax a Domain-Specific Language (DSL).
|
||||
|
||||
**Note:** Why do we use a macro to do this? Well it serves two purposes: first
|
||||
it makes expectations easily identifiable (either by `gsearch` or by a human
|
||||
reader), and second it allows gMock to include the source file location of a
|
||||
failed expectation in messages, making debugging easier.
|
||||
|
||||
### Matchers: What Arguments Do We Expect?
|
||||
|
||||
When a mock function takes arguments, we may specify what arguments we are
|
||||
expecting, for example:
|
||||
|
||||
```cpp
|
||||
// Expects the turtle to move forward by 100 units.
|
||||
EXPECT_CALL(turtle, Forward(100));
|
||||
```
|
||||
|
||||
Oftentimes you do not want to be too specific. Remember that talk about tests
|
||||
being too rigid? Over specification leads to brittle tests and obscures the
|
||||
intent of tests. Therefore we encourage you to specify only what's necessary—no
|
||||
more, no less. If you aren't interested in the value of an argument, write `_`
|
||||
as the argument, which means "anything goes":
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
// Expects that the turtle jumps to somewhere on the x=50 line.
|
||||
EXPECT_CALL(turtle, GoTo(50, _));
|
||||
```
|
||||
|
||||
`_` is an instance of what we call **matchers**. A matcher is like a predicate
|
||||
and can test whether an argument is what we'd expect. You can use a matcher
|
||||
inside `EXPECT_CALL()` wherever a function argument is expected. `_` is a
|
||||
convenient way of saying "any value".
|
||||
|
||||
In the above examples, `100` and `50` are also matchers; implicitly, they are
|
||||
the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be
|
||||
equal (using `operator==`) to the matcher argument. There are many
|
||||
[built-in matchers](gmock_cheat_sheet.md#MatcherList) for common types (as well
|
||||
as [custom matchers](gmock_cook_book.md#NewMatchers)); for example:
|
||||
|
||||
```cpp
|
||||
using ::testing::Ge;
|
||||
...
|
||||
// Expects the turtle moves forward by at least 100.
|
||||
EXPECT_CALL(turtle, Forward(Ge(100)));
|
||||
```
|
||||
|
||||
If you don't care about *any* arguments, rather than specify `_` for each of
|
||||
them you may instead omit the parameter list:
|
||||
|
||||
```cpp
|
||||
// Expects the turtle to move forward.
|
||||
EXPECT_CALL(turtle, Forward);
|
||||
// Expects the turtle to jump somewhere.
|
||||
EXPECT_CALL(turtle, GoTo);
|
||||
```
|
||||
|
||||
This works for all non-overloaded methods; if a method is overloaded, you need
|
||||
to help gMock resolve which overload is expected by specifying the number of
|
||||
arguments and possibly also the
|
||||
[types of the arguments](gmock_cook_book.md#SelectOverload).
|
||||
|
||||
### Cardinalities: How Many Times Will It Be Called?
|
||||
|
||||
The first clause we can specify following an `EXPECT_CALL()` is `Times()`. We
|
||||
call its argument a **cardinality** as it tells *how many times* the call should
|
||||
occur. It allows us to repeat an expectation many times without actually writing
|
||||
it as many times. More importantly, a cardinality can be "fuzzy", just like a
|
||||
matcher can be. This allows a user to express the intent of a test exactly.
|
||||
|
||||
An interesting special case is when we say `Times(0)`. You may have guessed - it
|
||||
means that the function shouldn't be called with the given arguments at all, and
|
||||
gMock will report a googletest failure whenever the function is (wrongfully)
|
||||
called.
|
||||
|
||||
We've seen `AtLeast(n)` as an example of fuzzy cardinalities earlier. For the
|
||||
list of built-in cardinalities you can use, see
|
||||
[here](gmock_cheat_sheet.md#CardinalityList).
|
||||
|
||||
The `Times()` clause can be omitted. **If you omit `Times()`, gMock will infer
|
||||
the cardinality for you.** The rules are easy to remember:
|
||||
|
||||
* If **neither** `WillOnce()` **nor** `WillRepeatedly()` is in the
|
||||
`EXPECT_CALL()`, the inferred cardinality is `Times(1)`.
|
||||
* If there are *n* `WillOnce()`'s but **no** `WillRepeatedly()`, where *n* >=
|
||||
1, the cardinality is `Times(n)`.
|
||||
* If there are *n* `WillOnce()`'s and **one** `WillRepeatedly()`, where *n* >=
|
||||
0, the cardinality is `Times(AtLeast(n))`.
|
||||
|
||||
**Quick quiz:** what do you think will happen if a function is expected to be
|
||||
called twice but actually called four times?
|
||||
|
||||
### Actions: What Should It Do?
|
||||
|
||||
Remember that a mock object doesn't really have a working implementation? We as
|
||||
users have to tell it what to do when a method is invoked. This is easy in
|
||||
gMock.
|
||||
|
||||
First, if the return type of a mock function is a built-in type or a pointer,
|
||||
the function has a **default action** (a `void` function will just return, a
|
||||
`bool` function will return `false`, and other functions will return 0). In
|
||||
addition, in C++ 11 and above, a mock function whose return type is
|
||||
default-constructible (i.e. has a default constructor) has a default action of
|
||||
returning a default-constructed value. If you don't say anything, this behavior
|
||||
will be used.
|
||||
|
||||
Second, if a mock function doesn't have a default action, or the default action
|
||||
doesn't suit you, you can specify the action to be taken each time the
|
||||
expectation matches using a series of `WillOnce()` clauses followed by an
|
||||
optional `WillRepeatedly()`. For example,
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.WillOnce(Return(100))
|
||||
.WillOnce(Return(200))
|
||||
.WillOnce(Return(300));
|
||||
```
|
||||
|
||||
says that `turtle.GetX()` will be called *exactly three times* (gMock inferred
|
||||
this from how many `WillOnce()` clauses we've written, since we didn't
|
||||
explicitly write `Times()`), and will return 100, 200, and 300 respectively.
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
EXPECT_CALL(turtle, GetY())
|
||||
.WillOnce(Return(100))
|
||||
.WillOnce(Return(200))
|
||||
.WillRepeatedly(Return(300));
|
||||
```
|
||||
|
||||
says that `turtle.GetY()` will be called *at least twice* (gMock knows this as
|
||||
we've written two `WillOnce()` clauses and a `WillRepeatedly()` while having no
|
||||
explicit `Times()`), will return 100 and 200 respectively the first two times,
|
||||
and 300 from the third time on.
|
||||
|
||||
Of course, if you explicitly write a `Times()`, gMock will not try to infer the
|
||||
cardinality itself. What if the number you specified is larger than there are
|
||||
`WillOnce()` clauses? Well, after all `WillOnce()`s are used up, gMock will do
|
||||
the *default* action for the function every time (unless, of course, you have a
|
||||
`WillRepeatedly()`.).
|
||||
|
||||
What can we do inside `WillOnce()` besides `Return()`? You can return a
|
||||
reference using `ReturnRef(*variable*)`, or invoke a pre-defined function, among
|
||||
[others](gmock_cook_book.md#using-actions).
|
||||
|
||||
**Important note:** The `EXPECT_CALL()` statement evaluates the action clause
|
||||
only once, even though the action may be performed many times. Therefore you
|
||||
must be careful about side effects. The following may not do what you want:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
int n = 100;
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.Times(4)
|
||||
.WillRepeatedly(Return(n++));
|
||||
```
|
||||
|
||||
Instead of returning 100, 101, 102, ..., consecutively, this mock function will
|
||||
always return 100 as `n++` is only evaluated once. Similarly, `Return(new Foo)`
|
||||
will create a new `Foo` object when the `EXPECT_CALL()` is executed, and will
|
||||
return the same pointer every time. If you want the side effect to happen every
|
||||
time, you need to define a custom action, which we'll teach in the
|
||||
[cook book](http://<!-- GOOGLETEST_CM0012 DO NOT DELETE -->).
|
||||
|
||||
Time for another quiz! What do you think the following means?
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
EXPECT_CALL(turtle, GetY())
|
||||
.Times(4)
|
||||
.WillOnce(Return(100));
|
||||
```
|
||||
|
||||
Obviously `turtle.GetY()` is expected to be called four times. But if you think
|
||||
it will return 100 every time, think twice! Remember that one `WillOnce()`
|
||||
clause will be consumed each time the function is invoked and the default action
|
||||
will be taken afterwards. So the right answer is that `turtle.GetY()` will
|
||||
return 100 the first time, but **return 0 from the second time on**, as
|
||||
returning 0 is the default action for `int` functions.
|
||||
|
||||
### Using Multiple Expectations {#MultiExpectations}
|
||||
|
||||
So far we've only shown examples where you have a single expectation. More
|
||||
realistically, you'll specify expectations on multiple mock methods which may be
|
||||
from multiple mock objects.
|
||||
|
||||
By default, when a mock method is invoked, gMock will search the expectations in
|
||||
the **reverse order** they are defined, and stop when an active expectation that
|
||||
matches the arguments is found (you can think of it as "newer rules override
|
||||
older ones."). If the matching expectation cannot take any more calls, you will
|
||||
get an upper-bound-violated failure. Here's an example:
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
...
|
||||
EXPECT_CALL(turtle, Forward(_)); // #1
|
||||
EXPECT_CALL(turtle, Forward(10)) // #2
|
||||
.Times(2);
|
||||
```
|
||||
|
||||
If `Forward(10)` is called three times in a row, the third time it will be an
|
||||
error, as the last matching expectation (#2) has been saturated. If, however,
|
||||
the third `Forward(10)` call is replaced by `Forward(20)`, then it would be OK,
|
||||
as now #1 will be the matching expectation.
|
||||
|
||||
**Note:** Why does gMock search for a match in the *reverse* order of the
|
||||
expectations? The reason is that this allows a user to set up the default
|
||||
expectations in a mock object's constructor or the test fixture's set-up phase
|
||||
and then customize the mock by writing more specific expectations in the test
|
||||
body. So, if you have two expectations on the same method, you want to put the
|
||||
one with more specific matchers **after** the other, or the more specific rule
|
||||
would be shadowed by the more general one that comes after it.
|
||||
|
||||
**Tip:** It is very common to start with a catch-all expectation for a method
|
||||
and `Times(AnyNumber())` (omitting arguments, or with `_` for all arguments, if
|
||||
overloaded). This makes any calls to the method expected. This is not necessary
|
||||
for methods that are not mentioned at all (these are "uninteresting"), but is
|
||||
useful for methods that have some expectations, but for which other calls are
|
||||
ok. See
|
||||
[Understanding Uninteresting vs Unexpected Calls](gmock_cook_book.md#uninteresting-vs-unexpected).
|
||||
|
||||
### Ordered vs Unordered Calls {#OrderedCalls}
|
||||
|
||||
By default, an expectation can match a call even though an earlier expectation
|
||||
hasn't been satisfied. In other words, the calls don't have to occur in the
|
||||
order the expectations are specified.
|
||||
|
||||
Sometimes, you may want all the expected calls to occur in a strict order. To
|
||||
say this in gMock is easy:
|
||||
|
||||
```cpp
|
||||
using ::testing::InSequence;
|
||||
...
|
||||
TEST(FooTest, DrawsLineSegment) {
|
||||
...
|
||||
{
|
||||
InSequence seq;
|
||||
|
||||
EXPECT_CALL(turtle, PenDown());
|
||||
EXPECT_CALL(turtle, Forward(100));
|
||||
EXPECT_CALL(turtle, PenUp());
|
||||
}
|
||||
Foo();
|
||||
}
|
||||
```
|
||||
|
||||
By creating an object of type `InSequence`, all expectations in its scope are
|
||||
put into a *sequence* and have to occur *sequentially*. Since we are just
|
||||
relying on the constructor and destructor of this object to do the actual work,
|
||||
its name is really irrelevant.
|
||||
|
||||
In this example, we test that `Foo()` calls the three expected functions in the
|
||||
order as written. If a call is made out-of-order, it will be an error.
|
||||
|
||||
(What if you care about the relative order of some of the calls, but not all of
|
||||
them? Can you specify an arbitrary partial order? The answer is ... yes! The
|
||||
details can be found [here](gmock_cook_book.md#OrderedCalls).)
|
||||
|
||||
### All Expectations Are Sticky (Unless Said Otherwise) {#StickyExpectations}
|
||||
|
||||
Now let's do a quick quiz to see how well you can use this mock stuff already.
|
||||
How would you test that the turtle is asked to go to the origin *exactly twice*
|
||||
(you want to ignore any other instructions it receives)?
|
||||
|
||||
After you've come up with your answer, take a look at ours and compare notes
|
||||
(solve it yourself first - don't cheat!):
|
||||
|
||||
```cpp
|
||||
using ::testing::_;
|
||||
using ::testing::AnyNumber;
|
||||
...
|
||||
EXPECT_CALL(turtle, GoTo(_, _)) // #1
|
||||
.Times(AnyNumber());
|
||||
EXPECT_CALL(turtle, GoTo(0, 0)) // #2
|
||||
.Times(2);
|
||||
```
|
||||
|
||||
Suppose `turtle.GoTo(0, 0)` is called three times. In the third time, gMock will
|
||||
see that the arguments match expectation #2 (remember that we always pick the
|
||||
last matching expectation). Now, since we said that there should be only two
|
||||
such calls, gMock will report an error immediately. This is basically what we've
|
||||
told you in the [Using Multiple Expectations](#MultiExpectations) section above.
|
||||
|
||||
This example shows that **expectations in gMock are "sticky" by default**, in
|
||||
the sense that they remain active even after we have reached their invocation
|
||||
upper bounds. This is an important rule to remember, as it affects the meaning
|
||||
of the spec, and is **different** to how it's done in many other mocking
|
||||
frameworks (Why'd we do that? Because we think our rule makes the common cases
|
||||
easier to express and understand.).
|
||||
|
||||
Simple? Let's see if you've really understood it: what does the following code
|
||||
say?
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
for (int i = n; i > 0; i--) {
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.WillOnce(Return(10*i));
|
||||
}
|
||||
```
|
||||
|
||||
If you think it says that `turtle.GetX()` will be called `n` times and will
|
||||
return 10, 20, 30, ..., consecutively, think twice! The problem is that, as we
|
||||
said, expectations are sticky. So, the second time `turtle.GetX()` is called,
|
||||
the last (latest) `EXPECT_CALL()` statement will match, and will immediately
|
||||
lead to an "upper bound violated" error - this piece of code is not very useful!
|
||||
|
||||
One correct way of saying that `turtle.GetX()` will return 10, 20, 30, ..., is
|
||||
to explicitly say that the expectations are *not* sticky. In other words, they
|
||||
should *retire* as soon as they are saturated:
|
||||
|
||||
```cpp
|
||||
using ::testing::Return;
|
||||
...
|
||||
for (int i = n; i > 0; i--) {
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.WillOnce(Return(10*i))
|
||||
.RetiresOnSaturation();
|
||||
}
|
||||
```
|
||||
|
||||
And, there's a better way to do it: in this case, we expect the calls to occur
|
||||
in a specific order, and we line up the actions to match the order. Since the
|
||||
order is important here, we should make it explicit using a sequence:
|
||||
|
||||
```cpp
|
||||
using ::testing::InSequence;
|
||||
using ::testing::Return;
|
||||
...
|
||||
{
|
||||
InSequence s;
|
||||
|
||||
for (int i = 1; i <= n; i++) {
|
||||
EXPECT_CALL(turtle, GetX())
|
||||
.WillOnce(Return(10*i))
|
||||
.RetiresOnSaturation();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
By the way, the other situation where an expectation may *not* be sticky is when
|
||||
it's in a sequence - as soon as another expectation that comes after it in the
|
||||
sequence has been used, it automatically retires (and will never be used to
|
||||
match any call).
|
||||
|
||||
### Uninteresting Calls
|
||||
|
||||
A mock object may have many methods, and not all of them are that interesting.
|
||||
For example, in some tests we may not care about how many times `GetX()` and
|
||||
`GetY()` get called.
|
||||
|
||||
In gMock, if you are not interested in a method, just don't say anything about
|
||||
it. If a call to this method occurs, you'll see a warning in the test output,
|
||||
but it won't be a failure. This is called "naggy" behavior; to change, see
|
||||
[The Nice, the Strict, and the Naggy](gmock_cook_book.md#NiceStrictNaggy).
|
||||
150
docs/pkgconfig.md
Normal file
150
docs/pkgconfig.md
Normal file
@@ -0,0 +1,150 @@
|
||||
## Using GoogleTest from various build systems
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
GoogleTest comes with pkg-config files that can be used to determine all
|
||||
necessary flags for compiling and linking to GoogleTest (and GoogleMock).
|
||||
Pkg-config is a standardised plain-text format containing
|
||||
|
||||
* the includedir (-I) path
|
||||
* necessary macro (-D) definitions
|
||||
* further required flags (-pthread)
|
||||
* the library (-L) path
|
||||
* the library (-l) to link to
|
||||
|
||||
All current build systems support pkg-config in one way or another. For all
|
||||
examples here we assume you want to compile the sample
|
||||
`samples/sample3_unittest.cc`.
|
||||
|
||||
### CMake
|
||||
|
||||
Using `pkg-config` in CMake is fairly easy:
|
||||
|
||||
```cmake
|
||||
cmake_minimum_required(VERSION 3.0)
|
||||
|
||||
cmake_policy(SET CMP0048 NEW)
|
||||
project(my_gtest_pkgconfig VERSION 0.0.1 LANGUAGES CXX)
|
||||
|
||||
find_package(PkgConfig)
|
||||
pkg_search_module(GTEST REQUIRED gtest_main)
|
||||
|
||||
add_executable(testapp samples/sample3_unittest.cc)
|
||||
target_link_libraries(testapp ${GTEST_LDFLAGS})
|
||||
target_compile_options(testapp PUBLIC ${GTEST_CFLAGS})
|
||||
|
||||
include(CTest)
|
||||
add_test(first_and_only_test testapp)
|
||||
```
|
||||
|
||||
It is generally recommended that you use `target_compile_options` + `_CFLAGS`
|
||||
over `target_include_directories` + `_INCLUDE_DIRS` as the former includes not
|
||||
just -I flags (GoogleTest might require a macro indicating to internal headers
|
||||
that all libraries have been compiled with threading enabled. In addition,
|
||||
GoogleTest might also require `-pthread` in the compiling step, and as such
|
||||
splitting the pkg-config `Cflags` variable into include dirs and macros for
|
||||
`target_compile_definitions()` might still miss this). The same recommendation
|
||||
goes for using `_LDFLAGS` over the more commonplace `_LIBRARIES`, which happens
|
||||
to discard `-L` flags and `-pthread`.
|
||||
|
||||
### Help! pkg-config can't find GoogleTest!
|
||||
|
||||
Let's say you have a `CMakeLists.txt` along the lines of the one in this
|
||||
tutorial and you try to run `cmake`. It is very possible that you get a failure
|
||||
along the lines of:
|
||||
|
||||
```
|
||||
-- Checking for one of the modules 'gtest_main'
|
||||
CMake Error at /usr/share/cmake/Modules/FindPkgConfig.cmake:640 (message):
|
||||
None of the required 'gtest_main' found
|
||||
```
|
||||
|
||||
These failures are common if you installed GoogleTest yourself and have not
|
||||
sourced it from a distro or other package manager. If so, you need to tell
|
||||
pkg-config where it can find the `.pc` files containing the information. Say you
|
||||
installed GoogleTest to `/usr/local`, then it might be that the `.pc` files are
|
||||
installed under `/usr/local/lib64/pkgconfig`. If you set
|
||||
|
||||
```
|
||||
export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig
|
||||
```
|
||||
|
||||
pkg-config will also try to look in `PKG_CONFIG_PATH` to find `gtest_main.pc`.
|
||||
|
||||
### Using pkg-config in a cross-compilation setting
|
||||
|
||||
Pkg-config can be used in a cross-compilation setting too. To do this, let's
|
||||
assume the final prefix of the cross-compiled installation will be `/usr`, and
|
||||
your sysroot is `/home/MYUSER/sysroot`. Configure and install GTest using
|
||||
|
||||
```
|
||||
mkdir build && cmake -DCMAKE_INSTALL_PREFIX=/usr ..
|
||||
```
|
||||
|
||||
Install into the sysroot using `DESTDIR`:
|
||||
|
||||
```
|
||||
make -j install DESTDIR=/home/MYUSER/sysroot
|
||||
```
|
||||
|
||||
Before we continue, it is recommended to **always** define the following two
|
||||
variables for pkg-config in a cross-compilation setting:
|
||||
|
||||
```
|
||||
export PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=yes
|
||||
export PKG_CONFIG_ALLOW_SYSTEM_LIBS=yes
|
||||
```
|
||||
|
||||
otherwise `pkg-config` will filter `-I` and `-L` flags against standard prefixes
|
||||
such as `/usr` (see https://bugs.freedesktop.org/show_bug.cgi?id=28264#c3 for
|
||||
reasons why this stripping needs to occur usually).
|
||||
|
||||
If you look at the generated pkg-config file, it will look something like
|
||||
|
||||
```
|
||||
libdir=/usr/lib64
|
||||
includedir=/usr/include
|
||||
|
||||
Name: gtest
|
||||
Description: GoogleTest (without main() function)
|
||||
Version: 1.10.0
|
||||
URL: https://github.com/google/googletest
|
||||
Libs: -L${libdir} -lgtest -lpthread
|
||||
Cflags: -I${includedir} -DGTEST_HAS_PTHREAD=1 -lpthread
|
||||
```
|
||||
|
||||
Notice that the sysroot is not included in `libdir` and `includedir`! If you try
|
||||
to run `pkg-config` with the correct
|
||||
`PKG_CONFIG_LIBDIR=/home/MYUSER/sysroot/usr/lib64/pkgconfig` against this `.pc`
|
||||
file, you will get
|
||||
|
||||
```
|
||||
$ pkg-config --cflags gtest
|
||||
-DGTEST_HAS_PTHREAD=1 -lpthread -I/usr/include
|
||||
$ pkg-config --libs gtest
|
||||
-L/usr/lib64 -lgtest -lpthread
|
||||
```
|
||||
|
||||
which is obviously wrong and points to the `CBUILD` and not `CHOST` root. In
|
||||
order to use this in a cross-compilation setting, we need to tell pkg-config to
|
||||
inject the actual sysroot into `-I` and `-L` variables. Let us now tell
|
||||
pkg-config about the actual sysroot
|
||||
|
||||
```
|
||||
export PKG_CONFIG_DIR=
|
||||
export PKG_CONFIG_SYSROOT_DIR=/home/MYUSER/sysroot
|
||||
export PKG_CONFIG_LIBDIR=${PKG_CONFIG_SYSROOT_DIR}/usr/lib64/pkgconfig
|
||||
```
|
||||
|
||||
and running `pkg-config` again we get
|
||||
|
||||
```
|
||||
$ pkg-config --cflags gtest
|
||||
-DGTEST_HAS_PTHREAD=1 -lpthread -I/home/MYUSER/sysroot/usr/include
|
||||
$ pkg-config --libs gtest
|
||||
-L/home/MYUSER/sysroot/usr/lib64 -lgtest -lpthread
|
||||
```
|
||||
|
||||
which contains the correct sysroot now. For a more comprehensive guide to also
|
||||
including `${CHOST}` in build system calls, see the excellent tutorial by Diego
|
||||
Elio Pettenò: https://autotools.io/pkgconfig/cross-compiling.html
|
||||
583
docs/primer.md
Normal file
583
docs/primer.md
Normal file
@@ -0,0 +1,583 @@
|
||||
# Googletest Primer
|
||||
|
||||
<!-- GOOGLETEST_CM0036 DO NOT DELETE -->
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
## Introduction: Why googletest?
|
||||
|
||||
*googletest* helps you write better C++ tests.
|
||||
|
||||
googletest is a testing framework developed by the Testing Technology team with
|
||||
Google's specific requirements and constraints in mind. Whether you work on
|
||||
Linux, Windows, or a Mac, if you write C++ code, googletest can help you. And it
|
||||
supports *any* kind of tests, not just unit tests.
|
||||
|
||||
So what makes a good test, and how does googletest fit in? We believe:
|
||||
|
||||
1. Tests should be *independent* and *repeatable*. It's a pain to debug a test
|
||||
that succeeds or fails as a result of other tests. googletest isolates the
|
||||
tests by running each of them on a different object. When a test fails,
|
||||
googletest allows you to run it in isolation for quick debugging.
|
||||
2. Tests should be well *organized* and reflect the structure of the tested
|
||||
code. googletest groups related tests into test suites that can share data
|
||||
and subroutines. This common pattern is easy to recognize and makes tests
|
||||
easy to maintain. Such consistency is especially helpful when people switch
|
||||
projects and start to work on a new code base.
|
||||
3. Tests should be *portable* and *reusable*. Google has a lot of code that is
|
||||
platform-neutral; its tests should also be platform-neutral. googletest
|
||||
works on different OSes, with different compilers, with or without
|
||||
exceptions, so googletest tests can work with a variety of configurations.
|
||||
4. When tests fail, they should provide as much *information* about the problem
|
||||
as possible. googletest doesn't stop at the first test failure. Instead, it
|
||||
only stops the current test and continues with the next. You can also set up
|
||||
tests that report non-fatal failures after which the current test continues.
|
||||
Thus, you can detect and fix multiple bugs in a single run-edit-compile
|
||||
cycle.
|
||||
5. The testing framework should liberate test writers from housekeeping chores
|
||||
and let them focus on the test *content*. googletest automatically keeps
|
||||
track of all tests defined, and doesn't require the user to enumerate them
|
||||
in order to run them.
|
||||
6. Tests should be *fast*. With googletest, you can reuse shared resources
|
||||
across tests and pay for the set-up/tear-down only once, without making
|
||||
tests depend on each other.
|
||||
|
||||
Since googletest is based on the popular xUnit architecture, you'll feel right
|
||||
at home if you've used JUnit or PyUnit before. If not, it will take you about 10
|
||||
minutes to learn the basics and get started. So let's go!
|
||||
|
||||
## Beware of the nomenclature
|
||||
|
||||
_Note:_ There might be some confusion arising from different definitions of the
|
||||
terms _Test_, _Test Case_ and _Test Suite_, so beware of misunderstanding these.
|
||||
|
||||
Historically, googletest started to use the term _Test Case_ for grouping
|
||||
related tests, whereas current publications, including International Software
|
||||
Testing Qualifications Board ([ISTQB](http://www.istqb.org/)) materials and
|
||||
various textbooks on software quality, use the term
|
||||
_[Test Suite][istqb test suite]_ for this.
|
||||
|
||||
The related term _Test_, as it is used in googletest, corresponds to the term
|
||||
_[Test Case][istqb test case]_ of ISTQB and others.
|
||||
|
||||
The term _Test_ is commonly of broad enough sense, including ISTQB's definition
|
||||
of _Test Case_, so it's not much of a problem here. But the term _Test Case_ as
|
||||
was used in Google Test is of contradictory sense and thus confusing.
|
||||
|
||||
googletest recently started replacing the term _Test Case_ with _Test Suite_.
|
||||
The preferred API is *TestSuite*. The older TestCase API is being slowly
|
||||
deprecated and refactored away.
|
||||
|
||||
So please be aware of the different definitions of the terms:
|
||||
|
||||
<!-- mdformat off(github rendering does not support multiline tables) -->
|
||||
|
||||
Meaning | googletest Term | [ISTQB](http://www.istqb.org/) Term
|
||||
:----------------------------------------------------------------------------------- | :---------------------- | :----------------------------------
|
||||
Exercise a particular program path with specific input values and verify the results | [TEST()](#simple-tests) | [Test Case][istqb test case]
|
||||
|
||||
<!-- mdformat on -->
|
||||
|
||||
[istqb test case]: http://glossary.istqb.org/en/search/test%20case
|
||||
[istqb test suite]: http://glossary.istqb.org/en/search/test%20suite
|
||||
|
||||
## Basic Concepts
|
||||
|
||||
When using googletest, you start by writing *assertions*, which are statements
|
||||
that check whether a condition is true. An assertion's result can be *success*,
|
||||
*nonfatal failure*, or *fatal failure*. If a fatal failure occurs, it aborts the
|
||||
current function; otherwise the program continues normally.
|
||||
|
||||
*Tests* use assertions to verify the tested code's behavior. If a test crashes
|
||||
or has a failed assertion, then it *fails*; otherwise it *succeeds*.
|
||||
|
||||
A *test suite* contains one or many tests. You should group your tests into test
|
||||
suites that reflect the structure of the tested code. When multiple tests in a
|
||||
test suite need to share common objects and subroutines, you can put them into a
|
||||
*test fixture* class.
|
||||
|
||||
A *test program* can contain multiple test suites.
|
||||
|
||||
We'll now explain how to write a test program, starting at the individual
|
||||
assertion level and building up to tests and test suites.
|
||||
|
||||
## Assertions
|
||||
|
||||
googletest assertions are macros that resemble function calls. You test a class
|
||||
or function by making assertions about its behavior. When an assertion fails,
|
||||
googletest prints the assertion's source file and line number location, along
|
||||
with a failure message. You may also supply a custom failure message which will
|
||||
be appended to googletest's message.
|
||||
|
||||
The assertions come in pairs that test the same thing but have different effects
|
||||
on the current function. `ASSERT_*` versions generate fatal failures when they
|
||||
fail, and **abort the current function**. `EXPECT_*` versions generate nonfatal
|
||||
failures, which don't abort the current function. Usually `EXPECT_*` are
|
||||
preferred, as they allow more than one failure to be reported in a test.
|
||||
However, you should use `ASSERT_*` if it doesn't make sense to continue when the
|
||||
assertion in question fails.
|
||||
|
||||
Since a failed `ASSERT_*` returns from the current function immediately,
|
||||
possibly skipping clean-up code that comes after it, it may cause a space leak.
|
||||
Depending on the nature of the leak, it may or may not be worth fixing - so keep
|
||||
this in mind if you get a heap checker error in addition to assertion errors.
|
||||
|
||||
To provide a custom failure message, simply stream it into the macro using the
|
||||
`<<` operator or a sequence of such operators. An example:
|
||||
|
||||
```c++
|
||||
ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
|
||||
|
||||
for (int i = 0; i < x.size(); ++i) {
|
||||
EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
|
||||
}
|
||||
```
|
||||
|
||||
Anything that can be streamed to an `ostream` can be streamed to an assertion
|
||||
macro--in particular, C strings and `string` objects. If a wide string
|
||||
(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
|
||||
streamed to an assertion, it will be translated to UTF-8 when printed.
|
||||
|
||||
### Basic Assertions
|
||||
|
||||
These assertions do basic true/false condition testing.
|
||||
|
||||
Fatal assertion | Nonfatal assertion | Verifies
|
||||
-------------------------- | -------------------------- | --------------------
|
||||
`ASSERT_TRUE(condition);` | `EXPECT_TRUE(condition);` | `condition` is true
|
||||
`ASSERT_FALSE(condition);` | `EXPECT_FALSE(condition);` | `condition` is false
|
||||
|
||||
Remember, when they fail, `ASSERT_*` yields a fatal failure and returns from the
|
||||
current function, while `EXPECT_*` yields a nonfatal failure, allowing the
|
||||
function to continue running. In either case, an assertion failure means its
|
||||
containing test fails.
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
### Binary Comparison
|
||||
|
||||
This section describes assertions that compare two values.
|
||||
|
||||
Fatal assertion | Nonfatal assertion | Verifies
|
||||
------------------------ | ------------------------ | --------------
|
||||
`ASSERT_EQ(val1, val2);` | `EXPECT_EQ(val1, val2);` | `val1 == val2`
|
||||
`ASSERT_NE(val1, val2);` | `EXPECT_NE(val1, val2);` | `val1 != val2`
|
||||
`ASSERT_LT(val1, val2);` | `EXPECT_LT(val1, val2);` | `val1 < val2`
|
||||
`ASSERT_LE(val1, val2);` | `EXPECT_LE(val1, val2);` | `val1 <= val2`
|
||||
`ASSERT_GT(val1, val2);` | `EXPECT_GT(val1, val2);` | `val1 > val2`
|
||||
`ASSERT_GE(val1, val2);` | `EXPECT_GE(val1, val2);` | `val1 >= val2`
|
||||
|
||||
Value arguments must be comparable by the assertion's comparison operator or
|
||||
you'll get a compiler error. We used to require the arguments to support the
|
||||
`<<` operator for streaming to an `ostream`, but this is no longer necessary. If
|
||||
`<<` is supported, it will be called to print the arguments when the assertion
|
||||
fails; otherwise googletest will attempt to print them in the best way it can.
|
||||
For more details and how to customize the printing of the arguments, see the
|
||||
[documentation](./advanced.md#teaching-googletest-how-to-print-your-values).
|
||||
|
||||
These assertions can work with a user-defined type, but only if you define the
|
||||
corresponding comparison operator (e.g., `==` or `<`). Since this is discouraged
|
||||
by the Google
|
||||
[C++ Style Guide](https://google.github.io/styleguide/cppguide.html#Operator_Overloading),
|
||||
you may need to use `ASSERT_TRUE()` or `EXPECT_TRUE()` to assert the equality of
|
||||
two objects of a user-defined type.
|
||||
|
||||
However, when possible, `ASSERT_EQ(actual, expected)` is preferred to
|
||||
`ASSERT_TRUE(actual == expected)`, since it tells you `actual` and `expected`'s
|
||||
values on failure.
|
||||
|
||||
Arguments are always evaluated exactly once. Therefore, it's OK for the
|
||||
arguments to have side effects. However, as with any ordinary C/C++ function,
|
||||
the arguments' evaluation order is undefined (i.e., the compiler is free to
|
||||
choose any order), and your code should not depend on any particular argument
|
||||
evaluation order.
|
||||
|
||||
`ASSERT_EQ()` does pointer equality on pointers. If used on two C strings, it
|
||||
tests if they are in the same memory location, not if they have the same value.
|
||||
Therefore, if you want to compare C strings (e.g. `const char*`) by value, use
|
||||
`ASSERT_STREQ()`, which will be described later on. In particular, to assert
|
||||
that a C string is `NULL`, use `ASSERT_STREQ(c_string, NULL)`. Consider using
|
||||
`ASSERT_EQ(c_string, nullptr)` if c++11 is supported. To compare two `string`
|
||||
objects, you should use `ASSERT_EQ`.
|
||||
|
||||
When doing pointer comparisons use `*_EQ(ptr, nullptr)` and `*_NE(ptr, nullptr)`
|
||||
instead of `*_EQ(ptr, NULL)` and `*_NE(ptr, NULL)`. This is because `nullptr` is
|
||||
typed, while `NULL` is not. See the [FAQ](faq.md) for more details.
|
||||
|
||||
If you're working with floating point numbers, you may want to use the floating
|
||||
point variations of some of these macros in order to avoid problems caused by
|
||||
rounding. See [Advanced googletest Topics](advanced.md) for details.
|
||||
|
||||
Macros in this section work with both narrow and wide string objects (`string`
|
||||
and `wstring`).
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
**Historical note**: Before February 2016 `*_EQ` had a convention of calling it
|
||||
as `ASSERT_EQ(expected, actual)`, so lots of existing code uses this order. Now
|
||||
`*_EQ` treats both parameters in the same way.
|
||||
|
||||
### String Comparison
|
||||
|
||||
The assertions in this group compare two **C strings**. If you want to compare
|
||||
two `string` objects, use `EXPECT_EQ`, `EXPECT_NE`, and etc instead.
|
||||
|
||||
<!-- mdformat off(github rendering does not support multiline tables) -->
|
||||
|
||||
| Fatal assertion | Nonfatal assertion | Verifies |
|
||||
| -------------------------- | ------------------------------ | -------------------------------------------------------- |
|
||||
| `ASSERT_STREQ(str1,str2);` | `EXPECT_STREQ(str1,str2);` | the two C strings have the same content |
|
||||
| `ASSERT_STRNE(str1,str2);` | `EXPECT_STRNE(str1,str2);` | the two C strings have different contents |
|
||||
| `ASSERT_STRCASEEQ(str1,str2);` | `EXPECT_STRCASEEQ(str1,str2);` | the two C strings have the same content, ignoring case |
|
||||
| `ASSERT_STRCASENE(str1,str2);` | `EXPECT_STRCASENE(str1,str2);` | the two C strings have different contents, ignoring case |
|
||||
|
||||
<!-- mdformat on-->
|
||||
|
||||
Note that "CASE" in an assertion name means that case is ignored. A `NULL`
|
||||
pointer and an empty string are considered *different*.
|
||||
|
||||
`*STREQ*` and `*STRNE*` also accept wide C strings (`wchar_t*`). If a comparison
|
||||
of two wide strings fails, their values will be printed as UTF-8 narrow strings.
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
**See also**: For more string comparison tricks (substring, prefix, suffix, and
|
||||
regular expression matching, for example), see [this](advanced.md) in the
|
||||
Advanced googletest Guide.
|
||||
|
||||
## Simple Tests
|
||||
|
||||
To create a test:
|
||||
|
||||
1. Use the `TEST()` macro to define and name a test function. These are
|
||||
ordinary C++ functions that don't return a value.
|
||||
2. In this function, along with any valid C++ statements you want to include,
|
||||
use the various googletest assertions to check values.
|
||||
3. The test's result is determined by the assertions; if any assertion in the
|
||||
test fails (either fatally or non-fatally), or if the test crashes, the
|
||||
entire test fails. Otherwise, it succeeds.
|
||||
|
||||
```c++
|
||||
TEST(TestSuiteName, TestName) {
|
||||
... test body ...
|
||||
}
|
||||
```
|
||||
|
||||
`TEST()` arguments go from general to specific. The *first* argument is the name
|
||||
of the test suite, and the *second* argument is the test's name within the test
|
||||
suite. Both names must be valid C++ identifiers, and they should not contain
|
||||
any underscores (`_`). A test's *full name* consists of its containing test suite and
|
||||
its individual name. Tests from different test suites can have the same
|
||||
individual name.
|
||||
|
||||
For example, let's take a simple integer function:
|
||||
|
||||
```c++
|
||||
int Factorial(int n); // Returns the factorial of n
|
||||
```
|
||||
|
||||
A test suite for this function might look like:
|
||||
|
||||
```c++
|
||||
// Tests factorial of 0.
|
||||
TEST(FactorialTest, HandlesZeroInput) {
|
||||
EXPECT_EQ(Factorial(0), 1);
|
||||
}
|
||||
|
||||
// Tests factorial of positive numbers.
|
||||
TEST(FactorialTest, HandlesPositiveInput) {
|
||||
EXPECT_EQ(Factorial(1), 1);
|
||||
EXPECT_EQ(Factorial(2), 2);
|
||||
EXPECT_EQ(Factorial(3), 6);
|
||||
EXPECT_EQ(Factorial(8), 40320);
|
||||
}
|
||||
```
|
||||
|
||||
googletest groups the test results by test suites, so logically related tests
|
||||
should be in the same test suite; in other words, the first argument to their
|
||||
`TEST()` should be the same. In the above example, we have two tests,
|
||||
`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
|
||||
suite `FactorialTest`.
|
||||
|
||||
When naming your test suites and tests, you should follow the same convention as
|
||||
for
|
||||
[naming functions and classes](https://google.github.io/styleguide/cppguide.html#Function_Names).
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
## Test Fixtures: Using the Same Data Configuration for Multiple Tests {#same-data-multiple-tests}
|
||||
|
||||
If you find yourself writing two or more tests that operate on similar data, you
|
||||
can use a *test fixture*. This allows you to reuse the same configuration of
|
||||
objects for several different tests.
|
||||
|
||||
To create a fixture:
|
||||
|
||||
1. Derive a class from `::testing::Test` . Start its body with `protected:`, as
|
||||
we'll want to access fixture members from sub-classes.
|
||||
2. Inside the class, declare any objects you plan to use.
|
||||
3. If necessary, write a default constructor or `SetUp()` function to prepare
|
||||
the objects for each test. A common mistake is to spell `SetUp()` as
|
||||
**`Setup()`** with a small `u` - Use `override` in C++11 to make sure you
|
||||
spelled it correctly.
|
||||
4. If necessary, write a destructor or `TearDown()` function to release any
|
||||
resources you allocated in `SetUp()` . To learn when you should use the
|
||||
constructor/destructor and when you should use `SetUp()/TearDown()`, read
|
||||
the [FAQ](faq.md#CtorVsSetUp).
|
||||
5. If needed, define subroutines for your tests to share.
|
||||
|
||||
When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
|
||||
access objects and subroutines in the test fixture:
|
||||
|
||||
```c++
|
||||
TEST_F(TestFixtureName, TestName) {
|
||||
... test body ...
|
||||
}
|
||||
```
|
||||
|
||||
Like `TEST()`, the first argument is the test suite name, but for `TEST_F()`
|
||||
this must be the name of the test fixture class. You've probably guessed: `_F`
|
||||
is for fixture.
|
||||
|
||||
Unfortunately, the C++ macro system does not allow us to create a single macro
|
||||
that can handle both types of tests. Using the wrong macro causes a compiler
|
||||
error.
|
||||
|
||||
Also, you must first define a test fixture class before using it in a
|
||||
`TEST_F()`, or you'll get the compiler error "`virtual outside class
|
||||
declaration`".
|
||||
|
||||
For each test defined with `TEST_F()`, googletest will create a *fresh* test
|
||||
fixture at runtime, immediately initialize it via `SetUp()`, run the test,
|
||||
clean up by calling `TearDown()`, and then delete the test fixture. Note that
|
||||
different tests in the same test suite have different test fixture objects, and
|
||||
googletest always deletes a test fixture before it creates the next one.
|
||||
googletest does **not** reuse the same test fixture for multiple tests. Any
|
||||
changes one test makes to the fixture do not affect other tests.
|
||||
|
||||
As an example, let's write tests for a FIFO queue class named `Queue`, which has
|
||||
the following interface:
|
||||
|
||||
```c++
|
||||
template <typename E> // E is the element type.
|
||||
class Queue {
|
||||
public:
|
||||
Queue();
|
||||
void Enqueue(const E& element);
|
||||
E* Dequeue(); // Returns NULL if the queue is empty.
|
||||
size_t size() const;
|
||||
...
|
||||
};
|
||||
```
|
||||
|
||||
First, define a fixture class. By convention, you should give it the name
|
||||
`FooTest` where `Foo` is the class being tested.
|
||||
|
||||
```c++
|
||||
class QueueTest : public ::testing::Test {
|
||||
protected:
|
||||
void SetUp() override {
|
||||
q1_.Enqueue(1);
|
||||
q2_.Enqueue(2);
|
||||
q2_.Enqueue(3);
|
||||
}
|
||||
|
||||
// void TearDown() override {}
|
||||
|
||||
Queue<int> q0_;
|
||||
Queue<int> q1_;
|
||||
Queue<int> q2_;
|
||||
};
|
||||
```
|
||||
|
||||
In this case, `TearDown()` is not needed since we don't have to clean up after
|
||||
each test, other than what's already done by the destructor.
|
||||
|
||||
Now we'll write tests using `TEST_F()` and this fixture.
|
||||
|
||||
```c++
|
||||
TEST_F(QueueTest, IsEmptyInitially) {
|
||||
EXPECT_EQ(q0_.size(), 0);
|
||||
}
|
||||
|
||||
TEST_F(QueueTest, DequeueWorks) {
|
||||
int* n = q0_.Dequeue();
|
||||
EXPECT_EQ(n, nullptr);
|
||||
|
||||
n = q1_.Dequeue();
|
||||
ASSERT_NE(n, nullptr);
|
||||
EXPECT_EQ(*n, 1);
|
||||
EXPECT_EQ(q1_.size(), 0);
|
||||
delete n;
|
||||
|
||||
n = q2_.Dequeue();
|
||||
ASSERT_NE(n, nullptr);
|
||||
EXPECT_EQ(*n, 2);
|
||||
EXPECT_EQ(q2_.size(), 1);
|
||||
delete n;
|
||||
}
|
||||
```
|
||||
|
||||
The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
|
||||
to use `EXPECT_*` when you want the test to continue to reveal more errors after
|
||||
the assertion failure, and use `ASSERT_*` when continuing after failure doesn't
|
||||
make sense. For example, the second assertion in the `Dequeue` test is
|
||||
`ASSERT_NE(nullptr, n)`, as we need to dereference the pointer `n` later, which
|
||||
would lead to a segfault when `n` is `NULL`.
|
||||
|
||||
When these tests run, the following happens:
|
||||
|
||||
1. googletest constructs a `QueueTest` object (let's call it `t1`).
|
||||
2. `t1.SetUp()` initializes `t1`.
|
||||
3. The first test (`IsEmptyInitially`) runs on `t1`.
|
||||
4. `t1.TearDown()` cleans up after the test finishes.
|
||||
5. `t1` is destructed.
|
||||
6. The above steps are repeated on another `QueueTest` object, this time
|
||||
running the `DequeueWorks` test.
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
## Invoking the Tests
|
||||
|
||||
`TEST()` and `TEST_F()` implicitly register their tests with googletest. So,
|
||||
unlike with many other C++ testing frameworks, you don't have to re-list all
|
||||
your defined tests in order to run them.
|
||||
|
||||
After defining your tests, you can run them with `RUN_ALL_TESTS()`, which
|
||||
returns `0` if all the tests are successful, or `1` otherwise. Note that
|
||||
`RUN_ALL_TESTS()` runs *all tests* in your link unit--they can be from
|
||||
different test suites, or even different source files.
|
||||
|
||||
When invoked, the `RUN_ALL_TESTS()` macro:
|
||||
|
||||
* Saves the state of all googletest flags.
|
||||
|
||||
* Creates a test fixture object for the first test.
|
||||
|
||||
* Initializes it via `SetUp()`.
|
||||
|
||||
* Runs the test on the fixture object.
|
||||
|
||||
* Cleans up the fixture via `TearDown()`.
|
||||
|
||||
* Deletes the fixture.
|
||||
|
||||
* Restores the state of all googletest flags.
|
||||
|
||||
* Repeats the above steps for the next test, until all tests have run.
|
||||
|
||||
If a fatal failure happens the subsequent steps will be skipped.
|
||||
|
||||
> IMPORTANT: You must **not** ignore the return value of `RUN_ALL_TESTS()`, or
|
||||
> you will get a compiler error. The rationale for this design is that the
|
||||
> automated testing service determines whether a test has passed based on its
|
||||
> exit code, not on its stdout/stderr output; thus your `main()` function must
|
||||
> return the value of `RUN_ALL_TESTS()`.
|
||||
>
|
||||
> Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than
|
||||
> once conflicts with some advanced googletest features (e.g., thread-safe
|
||||
> [death tests](advanced.md#death-tests)) and thus is not supported.
|
||||
|
||||
**Availability**: Linux, Windows, Mac.
|
||||
|
||||
## Writing the main() Function
|
||||
|
||||
Most users should _not_ need to write their own `main` function and instead link
|
||||
with `gtest_main` (as opposed to with `gtest`), which defines a suitable entry
|
||||
point. See the end of this section for details. The remainder of this section
|
||||
should only apply when you need to do something custom before the tests run that
|
||||
cannot be expressed within the framework of fixtures and test suites.
|
||||
|
||||
If you write your own `main` function, it should return the value of
|
||||
`RUN_ALL_TESTS()`.
|
||||
|
||||
You can start from this boilerplate:
|
||||
|
||||
```c++
|
||||
#include "this/package/foo.h"
|
||||
|
||||
#include "gtest/gtest.h"
|
||||
|
||||
namespace my {
|
||||
namespace project {
|
||||
namespace {
|
||||
|
||||
// The fixture for testing class Foo.
|
||||
class FooTest : public ::testing::Test {
|
||||
protected:
|
||||
// You can remove any or all of the following functions if their bodies would
|
||||
// be empty.
|
||||
|
||||
FooTest() {
|
||||
// You can do set-up work for each test here.
|
||||
}
|
||||
|
||||
~FooTest() override {
|
||||
// You can do clean-up work that doesn't throw exceptions here.
|
||||
}
|
||||
|
||||
// If the constructor and destructor are not enough for setting up
|
||||
// and cleaning up each test, you can define the following methods:
|
||||
|
||||
void SetUp() override {
|
||||
// Code here will be called immediately after the constructor (right
|
||||
// before each test).
|
||||
}
|
||||
|
||||
void TearDown() override {
|
||||
// Code here will be called immediately after each test (right
|
||||
// before the destructor).
|
||||
}
|
||||
|
||||
// Class members declared here can be used by all tests in the test suite
|
||||
// for Foo.
|
||||
};
|
||||
|
||||
// Tests that the Foo::Bar() method does Abc.
|
||||
TEST_F(FooTest, MethodBarDoesAbc) {
|
||||
const std::string input_filepath = "this/package/testdata/myinputfile.dat";
|
||||
const std::string output_filepath = "this/package/testdata/myoutputfile.dat";
|
||||
Foo f;
|
||||
EXPECT_EQ(f.Bar(input_filepath, output_filepath), 0);
|
||||
}
|
||||
|
||||
// Tests that Foo does Xyz.
|
||||
TEST_F(FooTest, DoesXyz) {
|
||||
// Exercises the Xyz feature of Foo.
|
||||
}
|
||||
|
||||
} // namespace
|
||||
} // namespace project
|
||||
} // namespace my
|
||||
|
||||
int main(int argc, char **argv) {
|
||||
::testing::InitGoogleTest(&argc, argv);
|
||||
return RUN_ALL_TESTS();
|
||||
}
|
||||
```
|
||||
|
||||
The `::testing::InitGoogleTest()` function parses the command line for
|
||||
googletest flags, and removes all recognized flags. This allows the user to
|
||||
control a test program's behavior via various flags, which we'll cover in
|
||||
the [AdvancedGuide](advanced.md). You **must** call this function before calling
|
||||
`RUN_ALL_TESTS()`, or the flags won't be properly initialized.
|
||||
|
||||
On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
|
||||
in programs compiled in `UNICODE` mode as well.
|
||||
|
||||
But maybe you think that writing all those `main` functions is too much work? We
|
||||
agree with you completely, and that's why Google Test provides a basic
|
||||
implementation of main(). If it fits your needs, then just link your test with
|
||||
the `gtest_main` library and you are good to go.
|
||||
|
||||
NOTE: `ParseGUnitFlags()` is deprecated in favor of `InitGoogleTest()`.
|
||||
|
||||
## Known Limitations
|
||||
|
||||
* Google Test is designed to be thread-safe. The implementation is thread-safe
|
||||
on systems where the `pthreads` library is available. It is currently
|
||||
_unsafe_ to use Google Test assertions from two threads concurrently on
|
||||
other systems (e.g. Windows). In most tests this is not an issue as usually
|
||||
the assertions are done in the main thread. If you want to help, you can
|
||||
volunteer to implement the necessary synchronization primitives in
|
||||
`gtest-port.h` for your platform.
|
||||
190
docs/pump_manual.md
Normal file
190
docs/pump_manual.md
Normal file
@@ -0,0 +1,190 @@
|
||||
<b>P</b>ump is <b>U</b>seful for <b>M</b>eta <b>P</b>rogramming.
|
||||
|
||||
<!-- GOOGLETEST_CM0035 DO NOT DELETE -->
|
||||
|
||||
# The Problem
|
||||
|
||||
Template and macro libraries often need to define many classes, functions, or
|
||||
macros that vary only (or almost only) in the number of arguments they take.
|
||||
It's a lot of repetitive, mechanical, and error-prone work.
|
||||
|
||||
Our experience is that it's tedious to write custom scripts, which tend to
|
||||
reflect the structure of the generated code poorly and are often hard to read
|
||||
and edit. For example, a small change needed in the generated code may require
|
||||
some non-intuitive, non-trivial changes in the script. This is especially
|
||||
painful when experimenting with the code.
|
||||
|
||||
This script may be useful for generating meta code, for example a series of
|
||||
macros of FOO1, FOO2, etc. Nevertheless, please make it your last resort
|
||||
technique by favouring C++ template metaprogramming or variadic macros.
|
||||
|
||||
# Our Solution
|
||||
|
||||
Pump (for Pump is Useful for Meta Programming, Pretty Useful for Meta
|
||||
Programming, or Practical Utility for Meta Programming, whichever you prefer) is
|
||||
a simple meta-programming tool for C++. The idea is that a programmer writes a
|
||||
`foo.pump` file which contains C++ code plus meta code that manipulates the C++
|
||||
code. The meta code can handle iterations over a range, nested iterations, local
|
||||
meta variable definitions, simple arithmetic, and conditional expressions. You
|
||||
can view it as a small Domain-Specific Language. The meta language is designed
|
||||
to be non-intrusive (s.t. it won't confuse Emacs' C++ mode, for example) and
|
||||
concise, making Pump code intuitive and easy to maintain.
|
||||
|
||||
## Highlights
|
||||
|
||||
* The implementation is in a single Python script and thus ultra portable: no
|
||||
build or installation is needed and it works cross platforms.
|
||||
* Pump tries to be smart with respect to
|
||||
[Google's style guide](https://github.com/google/styleguide): it breaks long
|
||||
lines (easy to have when they are generated) at acceptable places to fit
|
||||
within 80 columns and indent the continuation lines correctly.
|
||||
* The format is human-readable and more concise than XML.
|
||||
* The format works relatively well with Emacs' C++ mode.
|
||||
|
||||
## Examples
|
||||
|
||||
The following Pump code (where meta keywords start with `$`, `[[` and `]]` are
|
||||
meta brackets, and `$$` starts a meta comment that ends with the line):
|
||||
|
||||
```
|
||||
$var n = 3 $$ Defines a meta variable n.
|
||||
$range i 0..n $$ Declares the range of meta iterator i (inclusive).
|
||||
$for i [[
|
||||
$$ Meta loop.
|
||||
// Foo$i does blah for $i-ary predicates.
|
||||
$range j 1..i
|
||||
template <size_t N $for j [[, typename A$j]]>
|
||||
class Foo$i {
|
||||
$if i == 0 [[
|
||||
blah a;
|
||||
]] $elif i <= 2 [[
|
||||
blah b;
|
||||
]] $else [[
|
||||
blah c;
|
||||
]]
|
||||
};
|
||||
|
||||
]]
|
||||
```
|
||||
|
||||
will be translated by the Pump compiler to:
|
||||
|
||||
```cpp
|
||||
// Foo0 does blah for 0-ary predicates.
|
||||
template <size_t N>
|
||||
class Foo0 {
|
||||
blah a;
|
||||
};
|
||||
|
||||
// Foo1 does blah for 1-ary predicates.
|
||||
template <size_t N, typename A1>
|
||||
class Foo1 {
|
||||
blah b;
|
||||
};
|
||||
|
||||
// Foo2 does blah for 2-ary predicates.
|
||||
template <size_t N, typename A1, typename A2>
|
||||
class Foo2 {
|
||||
blah b;
|
||||
};
|
||||
|
||||
// Foo3 does blah for 3-ary predicates.
|
||||
template <size_t N, typename A1, typename A2, typename A3>
|
||||
class Foo3 {
|
||||
blah c;
|
||||
};
|
||||
```
|
||||
|
||||
In another example,
|
||||
|
||||
```
|
||||
$range i 1..n
|
||||
Func($for i + [[a$i]]);
|
||||
$$ The text between i and [[ is the separator between iterations.
|
||||
```
|
||||
|
||||
will generate one of the following lines (without the comments), depending on
|
||||
the value of `n`:
|
||||
|
||||
```cpp
|
||||
Func(); // If n is 0.
|
||||
Func(a1); // If n is 1.
|
||||
Func(a1 + a2); // If n is 2.
|
||||
Func(a1 + a2 + a3); // If n is 3.
|
||||
// And so on...
|
||||
```
|
||||
|
||||
## Constructs
|
||||
|
||||
We support the following meta programming constructs:
|
||||
|
||||
| `$var id = exp` | Defines a named constant value. `$id` is |
|
||||
: : valid until the end of the current meta :
|
||||
: : lexical block. :
|
||||
| :------------------------------- | :--------------------------------------- |
|
||||
| `$range id exp..exp` | Sets the range of an iteration variable, |
|
||||
: : which can be reused in multiple loops :
|
||||
: : later. :
|
||||
| `$for id sep [[ code ]]` | Iteration. The range of `id` must have |
|
||||
: : been defined earlier. `$id` is valid in :
|
||||
: : `code`. :
|
||||
| `$($)` | Generates a single `$` character. |
|
||||
| `$id` | Value of the named constant or iteration |
|
||||
: : variable. :
|
||||
| `$(exp)` | Value of the expression. |
|
||||
| `$if exp [[ code ]] else_branch` | Conditional. |
|
||||
| `[[ code ]]` | Meta lexical block. |
|
||||
| `cpp_code` | Raw C++ code. |
|
||||
| `$$ comment` | Meta comment. |
|
||||
|
||||
**Note:** To give the user some freedom in formatting the Pump source code, Pump
|
||||
ignores a new-line character if it's right after `$for foo` or next to `[[` or
|
||||
`]]`. Without this rule you'll often be forced to write very long lines to get
|
||||
the desired output. Therefore sometimes you may need to insert an extra new-line
|
||||
in such places for a new-line to show up in your output.
|
||||
|
||||
## Grammar
|
||||
|
||||
```ebnf
|
||||
code ::= atomic_code*
|
||||
atomic_code ::= $var id = exp
|
||||
| $var id = [[ code ]]
|
||||
| $range id exp..exp
|
||||
| $for id sep [[ code ]]
|
||||
| $($)
|
||||
| $id
|
||||
| $(exp)
|
||||
| $if exp [[ code ]] else_branch
|
||||
| [[ code ]]
|
||||
| cpp_code
|
||||
sep ::= cpp_code | empty_string
|
||||
else_branch ::= $else [[ code ]]
|
||||
| $elif exp [[ code ]] else_branch
|
||||
| empty_string
|
||||
exp ::= simple_expression_in_Python_syntax
|
||||
```
|
||||
|
||||
## Code
|
||||
|
||||
You can find the source code of Pump in
|
||||
[googlemock/scripts/pump.py](../googlemock/scripts/pump.py). It is still very
|
||||
unpolished and lacks automated tests, although it has been successfully used
|
||||
many times. If you find a chance to use it in your project, please let us know
|
||||
what you think! We also welcome help on improving Pump.
|
||||
|
||||
## Real Examples
|
||||
|
||||
You can find real-world applications of Pump in
|
||||
[Google Test](https://github.com/google/googletest/tree/master/googletest) and
|
||||
[Google Mock](https://github.com/google/googletest/tree/master/googlemock). The
|
||||
source file `foo.h.pump` generates `foo.h`.
|
||||
|
||||
## Tips
|
||||
|
||||
* If a meta variable is followed by a letter or digit, you can separate them
|
||||
using `[[]]`, which inserts an empty string. For example `Foo$j[[]]Helper`
|
||||
generate `Foo1Helper` when `j` is 1.
|
||||
* To avoid extra-long Pump source lines, you can break a line anywhere you
|
||||
want by inserting `[[]]` followed by a new line. Since any new-line
|
||||
character next to `[[` or `]]` is ignored, the generated code won't contain
|
||||
this new line.
|
||||
22
docs/samples.md
Normal file
22
docs/samples.md
Normal file
@@ -0,0 +1,22 @@
|
||||
# Googletest Samples {#samples}
|
||||
|
||||
If you're like us, you'd like to look at
|
||||
[googletest samples.](https://github.com/google/googletest/tree/master/googletest/samples)
|
||||
The sample directory has a number of well-commented samples showing how to use a
|
||||
variety of googletest features.
|
||||
|
||||
* Sample #1 shows the basic steps of using googletest to test C++ functions.
|
||||
* Sample #2 shows a more complex unit test for a class with multiple member
|
||||
functions.
|
||||
* Sample #3 uses a test fixture.
|
||||
* Sample #4 teaches you how to use googletest and `googletest.h` together to
|
||||
get the best of both libraries.
|
||||
* Sample #5 puts shared testing logic in a base test fixture, and reuses it in
|
||||
derived fixtures.
|
||||
* Sample #6 demonstrates type-parameterized tests.
|
||||
* Sample #7 teaches the basics of value-parameterized tests.
|
||||
* Sample #8 shows using `Combine()` in value-parameterized tests.
|
||||
* Sample #9 shows use of the listener API to modify Google Test's console
|
||||
output and the use of its reflection API to inspect test results.
|
||||
* Sample #10 shows use of the listener API to implement a primitive memory
|
||||
leak checker.
|
||||
Reference in New Issue
Block a user